Light - Reflection & Refraction in 1 Shot - Everything Covered || Class 10th Board || Pure English

0:00 hey guys welcome to this amazing platform of PW my name is rishabh your physics teacher and in today's lecture we are we are going to have one short revision of light reflection and refraction so guys in this chapter we will be starting with all the topics like plane mirror spherical mirror spherical lenses power refraction all these topics will be covered in this lecture so guys starting from the four main topics we will be starting with the reflection of light first how light is reflected from various surfaces from plane mirror from plane surfaces laws of reflection we will be discussing in this topic then we will be moving to the spherical mirror and its image formation like we have concave mirror we have convex mirror how do they form the image

0:46 what how do we calculate the image distance object distance all those things will be covered in this topic then we will be moving to the refraction of light refraction means bending of light when light passes from one medium to another it's a medium change is its speed changes right so we will be discussing all these factors in very very detail and at last we will be covering with the spherical lenses how does the lenses from the image how does light Ray Bend when it passes through any lens and lens formula power all those things so guys this lecture is going to be very very interesting right we will be discussing each and everything in very much detail okay guys so let's just start with the session now excited okay so guys first is corpuscular theory of light see

1:32 basically in 18th or 19th centuries we had a you know a scientist like Newton right Maxwell many phases were there right who studied the nature of the light so first of all Newton was there he gave us the corpuscular theory of flight corpuscular means the particles so he said that when light emerges from any Source this is our sun so you can see when light emerged from any Source basically it releases the Corpus calls Corpus calls means the particle of light so for example when light is emerging from any bulb or any tube light it it the particles of light are released right because it shows that the light has a particle nature and those

2:17 particles are known as corpuscals corpuscals means particles of light so this was given to us by Sir Isaac Newton particles of light so light emerges in the form of Corpus calls from any source so this theory is known as corpuscular theory of light right so guys many phenomena are based on this corpuscular Theory the particle of light are also known as photons you can also call them photons nowadays we call them we also basically these are more known by a name of photons the particles of light okay guys so there are many many experiments based on this corpuscular Theory or the particle theory of light for example sample solar cell solar cell basically Works under that photoelectric effect

3:04 you will study this effect detail in the higher classes but that solar cell what can I tell you at this level is solar cell works on the particle theory of light on the photon this theory of light right so many are many many experiments are there which prove the particle theory of light okay guys is it clear now okay so next is rectilinear propagation of right rectilinear means travel in a straight line rectilinear means travels travels in a straight line travels in a straight line now what does this Theory gives us see let us consider by an example suppose you have taken three cardboards right align them in a

3:49 line right there with a hole at the center of each of the cardboards right guys now you have replaced a candle here and you are observing this candle from here so guys you can see since all the holes are aligned along the same line the light from the candle is reaching to your eye so you can see the candle basically you you can see the candle here right but if I talk about any other Ray not passing through this hole so you can see you won't be able to get this Ray this Ray is not reaching to you this Ray is not reaching to you so guys what is happening right you won't be getting the image through this Ray or you can also call suppose if I displace this cardboard let's say if I

4:35 displace this middle cardboard by a certain distance so guys now are the holes along the same line now all these hole are along the same line obviously not the holes are not along the same line so now will you be able to look at this candle if I displace this cardboard a little bit obviously not why because light travels in a straight line it's not like light travel like this and it will go like this and you can see the candle note this won't happen this won't happen okay this won't happen because light travels in a straight line this experiment proves that light travels in a straight line okay this is known as a rectilinear propagation propagate means to travel what do you

5:23 mean by propagation propagation means to travel from one place to another propagate for example light waste propagate light from the sun is propagating to the Earth Sound Energy also propagate so this is known as the rectilinear propagation of light okay guys so what is the conclusion that light always travels in a straight line is it clear so guys many many theories were there given by many many scientists okay now let's start with the reflection let's our main topic now we are heading into the core of this chapter known as the reflection so guys you all see your yourself in the mirror in the morning you groom yourself right so how do you see yourself in the mirror have you ever thought thought of that how do however

6:09 image is formed in the mirror we all look ourselves in the mirror in the plane mirror in our houses so we see that we see the exact copy of ourselves in the plain mirror we see the exact copy of ourselves right guys for example this man is observing His Image this man is observing his mini image so you can see we have taken a plane mirror we have taken a plane mirror so have you ever thought how does this image forms this mirror forms the image of this man this is our object this is our object and this is the image this is the image so how does this mirror form the image of this object have you ever thought thought of this the answer lies in the

6:55 reflection the answer to this question is by reflection of light light is reflected by this mirror light is reflected by this mirror and thus this mirror forms the image basically so image is formed due to the reflection of light in the plane mirror it's not we are not done yet we will be discussing how is the Rays formed how are the Rays meeting we will also discuss that okay guys so basically what is reflection of light first we should go through the definition reflection of light is the phenomena of bouncing back of light bouncing back right for example when I drop a ball from here it goes down and bounce back to the floor and comes into my hand so

7:40 this is the bouncing back right if I throw a ball to the wall it bounces back towards me so this is how light is bounced back from any surface reflection of light is the bouncing back of light in the same medium same medians means suppose what do you mean by say medium suppose I have taken a plane mirror and to the right I have water right and in to the left I have air so guys if a ray is incident on this plane mirror it will be reflected in air it won't go in water in reflection light Ray comes back in the same medium it won't go in the water it is still in the air so this is our instant Ray right this is our incident Ray

8:28 this is our incident Ray and this is our reflected ray this is our reflected ray so both lie in the same medium medium doesn't change in reflection it changes in refraction we will study this later okay guys so incident Ray and reflected ray both lie in the same medium this is what is meant by refraction right and how does light Ray reflected when it strike a surface of any object guys reflection does not depend on the object every object reflects the light this board this remote this pen I even I am reflecting some light that's why you are able to see me so every object that reflects light we are able to see that

9:14 object is it clear so this is known as a reflection of light write down this definition guys just pause the video write it down then replay it okay clear reflection of light now are there certain laws that is that are followed by the reflection of light yes guys reflection we have certain laws for reflection it's not like we can reflect the light anywhere we want there is some law that has to be followed while the studying the reflection of light what is the law guys see suppose I have taken a plane mirror or any plane surface I have taken a plane mirror or any plane surface guys this is the incident Ray this is our incident Ray

10:03 guys this is normal what is normal guys normal means this is the point of incidence if I talk about point of incidence means the point at which incident Ray is meeting the surface this surface so this is called point of incidence point of incidence guys so this surface has reflected this light towards the hair right towards here so this is our reflected ray this is our reflected ray so guys basically we have three things first is incident Ray second is normal normal means the any line drawn I repeat any line drawn at

10:49 the point of incidence normal to the surface normal means at 90 degree so if I draw any line 90 degree to the surface at the point of incidence that line is said to be normal and this is our reflected ray so guys first what is the first law what is the first law first law states that this angle of incidence and angle of reflection I is the angle of incidence I is the angle of incidence guys I is the angle of incidence okay what is r guys R is the angle of reflection R is the angle of reflection so basically these

11:34 two angles are equal this is our first law of reflection it states that the angle of incidence is always equal to the angle of reflection both are same if I is 30 R is 30 degree if I is 40 degree R has to be 40 degree it's not like if r i is 30 R could be 40 right if if that is happening it it won't be a reflection of light we won't consider it as reflection of light always this law is followed clear okay guys now what is the next law this is the first part of this law next part is the incident Ray the normal and to the mirror at the point of incidence I I said 90 degree to the uh that mirror at

12:20 the point and the reflected ray all lie in same plane now what is same plane what do you mean by simply plane means two dimensional surface what do you mean by plane plane means any surface having two dimensions for example this smart board this smart board currently is a plane surface right or for example or for example if I talk about the plane of the paper the paper of the node of paper in your notebook it's also plane surface if I if I neglect its width right its height so it's a plane surface so this is two dimensional surface so basically what is the second listen to me very very carefully people don't that get this

13:05 incidentally normal to the mirror and the point of incident right and the reflected ray all these three lie in the same plane now what do you mean by same plane plane means all these lie in the same plane like I have a wiper of a car have you have you observed the wiper of a car it moves like this it won't move like this now it won't move it won't move like this it moves in a plane It Moves In One Direction in one along one surface so this is the basically thing is incident Ray normal Ray for example I am moving like a Viper my hand so I'm starting from here incident Ray normal Ray reflected ray can you see the motion is in one go right it's moving like a wiper of a car so these

13:53 these the all these three Ray should come in this plane it it's not like incident and in normal I like this and reflected is coming out of the board it won't happen all lag right like a wiper of a car clear you can remember this second Point like this okay so all these three light rays incident normal and the reflected ray all lie in the same plane is it clear guys so these are the laws of reflection of light these are the laws of reflection of light clear write it down fast okay now so most important plane mirror image formation by a plane mirror so guys can You observe this cat can You observe

14:38 this cat see this is the cat and this cat is observing herself in the mirror you must have seen many animals like dogs and all those observing themselves in the mirror and getting scared so basically this cat is observing herself in this mirror this is our plane mirror this is what guys this is our plain mirror okay so this is our card this is our image basically this is the image this is the image so guys can you see the motion in the object are same as the motion in the image the way the cat is moving is same as the way its image is moving see the cat is head is coming down head is coming down the head of the image is also coming down right can you

15:24 see it right the motion in the hand of the object the and the motion in the hand of the image are same the hand is coming down right you can see the hand will move like this see the hand is coming up and the Hand of the image is coming up so basically what is happening both are copying each other the object and the image are copying each other in plane mirror so this is what happens here this is what happens here that is foreign mirror in plane mirror image and object image and object are what are replica of each other

16:09 r word r replica of each other means copy of each other there the both will copy each other for example obviously when we look ourselves in the mirror also the image and the object are copy of each other right guys so you can see this is what happens in the plane mirror so plain mirror creates the exact replica the exact copy of the object is it clear okay so guys okay we have another sir now go write one more research sir even two more receptor so guys this is myself right this is real me this is the plane mirror I am observing myself in the plane mirror I am observing myself in the plane mirror now I I will tell you the characteristics of the image formed

16:55 right so guys can you tell me the I am looking forward in the plane mirror like this so I am looking to my right hand this is my right hand this is my right hand right this is me and this is my right hand but guys if I talk about my image so you can see my right hand has become my left hand in the image this is the left hand of my image in a right hand my right hand has become my left hand right and my left hand will become my right hand so what is happening right and left are reversing right and left are reversing so guys this is known as literal inversion literal inversion so this is what happens in the plane mirror the image is

17:42 literally inverted right to left and left to right right to left or left to right so this is what happens in the plane mirror this is known as lateral inversion right so this is the first characteristics of the image formed by the plane mirror there are many more characteristics we will study that is it clear okay so images literally inverted now we have another recipe haha so guys now I'm I'm about to tell you how my image is formed in the mirror see I have taken two rays for one from my head right so basically this Ray is normally incident so it will retrace its

18:28 path another Ray will be reflected right this is our angle of incidence normal with the normal this is angle of reflection and both will be same so Guys these two rays are not meeting here but if I back extend them you can see the image of my head is formed here 3 image is formed where reflected rays meet let me tell you one thing image is formed image is formed where where reflected Rays meat people sometimes gets confused where reflected rays are made where reflected rays

19:14 are meat image is formed at the point where reflected rays are made similarly if I talk about the ray from my toes so again same race and you can see my image is formed here so my complete image is formed like this there are many many Rays coming from my body parts from my body and therefore it their images corresponding image is formed by the mirror so this is a basic example of how plain mirror forms are image okay guys clear now notice one thing this is object basically this is real me right this is the object okay and this is the image this is the image right sorry it's virtual or I must say

20:00 it's image I will tell you the meaning of virtual don't worry right it's image so guys basically we have two parameters one is object distance another is image distance or what is object distance the distance of the object from the mirror is known as object distance I repeat the distance of the object from the mirror is known as object distance and the distance of the image from the mirror is known as image distance so guys in case of plane mirror can you notice one thing that object and image distance are same they are equal that is as the image is formed as far behind the mirror add the object is in

20:46 front right you have you observed suppose you are standing in front of a plane mirror so do this right now if you move away from the mirror your image will also go to away from you in the mirror if you move yourself away from the mirror yeah right so your image in the mirror will also go away from you or if you are moving towards the plane mirror your image will also move towards you have you observed this right in the mirror so that means image and object distance are equal they are changing equally so this is the second characteristics image distance on object distance are same in case of plane mirror now there is one more thing basically this image is called virtual image this

21:35 image is called virtual image now what is virtual image guys what is virtual image let me tell you see basically what happens is if I talk about reflected Rays these two rays will never meet here because they are diverging the reflected Rays right they won't actually meet but if I back extend them I can see the image so guys this is the virtual image virtual means behind the mirror the image is formed behind the mirror the rays are not actually in meat but the Rays appear to meet right if I am looking over this Ray suppose I am looking myself I am looking myself or somebody is looking at me from here so he will see me here he will see my image here so basically it's a virtual image

22:20 right he will see me here it's a virtual image the rays are the images from behind the mirror first thing second is raise won't actually meet this is the case right but if the Rays actually meet this is known as the real image we will see the real image in the coming spherical mirrors but for this plane mirror always forms the virtual image can't be taken on a screen you cannot take this image on the screen because it's virtual okay guys is it clear fine and one more thing one more thing am I magnified this is the height of real me can you see the height of myself and my image are same can you see one more thing my height and my image height are

23:06 same and that is obvious the when we see ourselves in the mirror our height is same as the height of the image voters equal in hand it's not like my height is my image is magnified it has become too large or and has gone too small this does not happen in plane mirror it too happens in spherical mirrors but it does not happen in the plane mirror they form the same size image is it clear guys now let let's write down all the points write down all the points guys first is image found by plane mirror is always virtual and erect now what do you mean by erect erect means the object is like this and the image is also formed like this it is not upside down if my head is upwards obviously the head of my image

23:51 is upwards right it's not like now my image will be inverted it won't get inverted is it clear eyes so image is always virtual and erect next point is the size of the image is equal to the size of the object object height and image height are same what is the meaning of this point is that object and image height are same object and image height are same is it clear guys is it clear okay what is third the image formed is as far behind the mirror as the object is in front of it that is object distance is equal to the image distance

24:38 clear and what is the last image is literally inverted right to left and left to right so Guys these are the four properties of the image formed by a plane mirror is it clear to you is it clear to you everybody so just write it down pause the video and write it down then we will move on to the next topic clear shall move forward now okay try this question read it read it guys question is a ray of light is incident on a plane mirror and gets reflected right the angle between read it carefully the angle between the incident Ray and the reflected ray is 120 degree the angle between instant and the reflected

25:23 ray is 120 degree what you have to find what is the angle of reflection you have to find the angle of reflection try just pause the video and try it first you should try the question by yourself then look over the solution right so guys let me draw a diagram diagram is must the more clear you draw the diagram you write the more you know you will be able to get the correct answer so basically this is the incident Ray and this is the reflected ray now it has been stated the angle between incident and the reflected ray is 120 degree so guys this angle is given as 120 degree this is angle of incidence this is angle of reflection this is normal this is I this is r and the total is 120

26:12 degree that is guys if you look from the figure I angle I plus angle R is 120 degree okay guys now I is equal to R yes can you recall the law of reflection I is equal to R so guys this will be twice of I is equals to 120 degree so guys what is I air I is 120 by 2 which is 60 degree each and this will also be equal to R so i and r are both equal to 60 degree clear so what is the correct option option b i and r both are equal to 60 degree clear guys very very basic question clear

26:57 write it down then we will move on okay let's move on now the this was a basic thing about the plane minutes but are there always plane mirror available to us it's not like that thing is sometimes we need to magnify the image guys it's not like we always form want the same size image sometimes we need to magnify the image magnify means either too large image or two small image so how does the how does it can happen right how does it happen basically thing is suppose if I you can you look at it the view of the complete field is taken in this small mirror can you see it this

27:45 view of this complete ground is taken in this small mirror now obviously it won't be plain mirror because you cannot taken the field this complete field in small mirror if the mirror would have been very very huge right but it's a small mirror and you have taken the view of the complete field so guys such mirrors are called spherical mirror spherical means their surface their reflecting surface is not plane they are spherical they are curved mirrors or they basically magnify the image so we can get the magnified image with the help of plain mirrors with the help of plane mirror sorry the spherical mirrors so what is the definition guys the reflecting surface of such mirrors can

28:32 be considered to form a part of the surface of hollow sphere basically what happens is if you take a hollow sphere guys suppose you take a hollow sphere you cut it from here right obviously now you will be getting a part like this now if you polish from outside it will act like a mirror basically what you have done you have polished it this is the polyps polished surface therefore if this is the polished surface this will be reflecting surface guys can you see it this will be reflecting surface so such mirror are called spherical mirror they are formed from sphere they form a part of the

29:18 sphere of glass when you paint it right and next is for such mirrors image size may or may not be equal to object size image can be larger than object image can be smaller than object image can also be equal to object so you can get a variety of images from these spherical mirrors now we will start we will be studying about these spherical mirror in very very detail is it clear write it down guys okay so we have two types of spherical mirror as I had said if you cut the glass fair either you can polish inside or you can polish outside right here you have polished inside here you have polished outside so this is the reflecting surface here and here this is

30:05 the reflecting surface so you can see reflecting surface are different here it is inverse here it is outward so guys based on this we have two types of spherical mirrors first is concave concave means it has inner reflecting surface the reflecting surface of concave mirror is inner but for convex outer surface is reflective outer surface is reflective inner is polished here energy inner is reflective outer is polished is it clear guys so we have two types of weather one is concave other is convex so how can you remember this concave means give like a cave it is bulged inwards it is bulged inwards it

30:51 is the reflecting surface is bulged inwards but here the reflecting surface is buzzed outwards it is burst outwards is it clear guys so we have two types of spherical mirror now we will be studying the property of each of the mirror in very very detail so guys basically there are certain terms before going see we will be moved we have gone through the definitions now we have to study the image formation that is that's why we are going through this so but before studying the image formation there are certain terms that needs to be cleared right so those terms we will be studying now first is Aperture what is Aperture it is the diameter of

31:37 the reflecting surface of spherical mirror diameter guys for example if I take two minutes let's take an example this is the first mirror and let's say this is the second mirror so guys what do you think which will reflect more light obviously this one this can reflect or this can gather more light right this can gather more light here we have less reflection this can gather more light right therefore it has more reflection here we have less reflection so guys this term is this is defined by the aperture a person means the reflecting area the reflecting surface area the reflecting

32:23 surface area this is known as aperture how much is the reflecting the effective diameter of this surface the affecting area of the surface clear this is known as the aperture this is how we Define the aperture okay guys so Moon aperture means more light rays will be gathered more light Ray will be gathered means the image will be more bright more clear so have you seen that that that have a very large mirrors they are observing to observe the space they are very very huge why the mirrors and lenses are very very huge the Hubble telescope and we have many many telescope in USA so basically the the effective diameter is very very large why to gather as much light as they can for example we had observed the image of

33:11 black hole few years back you must have all seen that so basically to observe that we we had we have a very very high technological telescope very very high effective the aperture telescope for that right guys to gather much many areas and two so that so as to get a clear picture of that okay guys next is Center of curvature so guys I had told you this spherical mirror is formed from a glass sphere so guys this glass Fair must be having some center now this glassware must be having some Center so this Center is known as this Center of curvature or the radius is known as the radius of curvature so what is Center of curvature the reflecting surface of a

33:56 spherical mirror forms a part of a sphere it is formed from the sphere and the that's the center of that sphere is known as the center of curvature is it clear right is it a center known as Center of curvature now it has to be some there has to be some radius also it has some radius now this sphere has some radius so this is known as the radius of curvature the radius of the sphere of which the reflecting surface of a spherical mirror forms a part the radius of that sphere this reflecting this glass sphere is known as the radius of this radius of curvature clear okay guys now we have principal access what is principal access C is

34:43 basically see before studying the principal access let me tell you few more terms then you will get it more clearly principal access now next is principal Focus principle Focus what is principle Focus guys C suppose if I take a concave mirror okay and some rays are coming parallel to principal axis like this rays are coming parallel to principal axis so guys after Reflection from the mirror they will meet at a point they will meet at a point right this point is known as the principal Focus where parallel Rich converge this is known as the converging mirror right you can see it is converging the Rays this

35:28 is known as the converging mirror is it clear so what is principle focus a number of rays parallel to the principal axis basically principle axis means this straight line right you will get when I when it about when I'm I will be telling you about the pole then you will get it more clearly basically it's a straight line so this green one this yellow rays are parallel to the green one so this is principal axis so when a number of parallel rays are falling on this mirror they meet at a point after reflection and this point is called principal Focus principle focus is it clear okay next is focal length focal length means C this is f right so focal and mean this is the pole

36:15 this is pole so focal length means distance between focus and the pole what is pole it is the center of the reflecting surface this e basically thing is this reflecting surface has a center this reflecting surface has a center and this Center is known as the pole we denote it by capital P is it clear okay so distance between the pole and the principal focus is known as the focal length clear guys now what is principle axis principle axis is an an imaginary straight line you imagine a straight line passing through the pole and the center of curvature of a spherical mirror imaginary straight line suppose if I draw any mirror if I draw any

37:03 mirror so guys basically we have pole we have Focus we have Center of curvature and this imaginary straight line is called principal axis the line joining all these three points right this is called principal axis these three points are collinear they lie along the same line and this line is known as principle axis is it clear guys so these are the terms related to any spherical mirror so guys it's not like these are for the concave mirror you can also have the same terms for convex mirror also guys so if I draw any convex mirror so this is our pole it is our focus and this is our Center of

37:48 curvature C okay guys basically here all lie to the right hand side because Central curvature will be here this mirror is formed like this basically this is formed like this right its radius of curvature lie to the right it the radius of curvature of concave mirror lies to the left clear guys so these are the terms related to the concave mirror you should be remembering principal Focus Center of curvature focal length right or radius of curvature pole aperture principal axis because these will you will be needing all these things in the image formations clear guys okay write down all these terms the definition these the definition of these terms is asked in the board Examination for example Define

38:34 Center of curvature I can recall my board examination I had a question on this defined principle axis Define principle axis and this defined Center of curvature I can still recall so that was three marker question I guess so I had to write down a definition of both these so thing is if you write these definitions you will get full marks right because these are exact exact definitions from ncrt is it clear should I move forward now write it down okay now image formation basically guys to study the image formation we should be knowing how to draw the Rays right because rate should meet I had told you where reflective light rays meet the image is formed at

39:20 that point but thing is how can we take the image which the Rays the arrays for image formation we should be knowing that so guys there are basically three rays that you can take three rays that you can take which I am about to tell you first is any Ray passing through principal Focus what happens if you if you pass any Ray through principal Focus guys this is principal axis this is pole this is focus this is Center of curvature if you pass any Ray through principal Focus guys it will become parallel to principle Axis or vice versa if you pass any rate through focus it will become parallel to principal Axis

40:05 or if you pop if you take any parallel Ray if you take any parallel I repeat if you take any rape parallel to principal axis it will pass through principal Focus so both are same array has to pass through F simple whether it is passing F first or whether it is it is it has gone become a parallel first it doesn't matter thing is it should be passing through Focus clear guys okay next is Ray passing through Center of curvature so guys if I pass any Ray through Center of curvature let me draw a different diagram for this if I pass any rate this is our pole this

40:53 is focus this is Center of curvature I will also draw this for convex mirror don't worry so guys basically if you pass any rate through Center of curvature it will retrace its path it will retrace its path why because see can you recall the clean mirror case any Ray normal to the mirror retraces its path we know this so guys basically anyway passing through Center of curvature is normal to the mirror that's why it retraces its path this is the case why because this Ray is normal to the Mirror is normal to the mirror is it clear that's why it retraces its path okay here angle of incidence is zero

41:39 right because it is along the normal and angle of reflection is also zero for Ray passing through C just recall this it is very very important can be asked i and r are 0 for array passing through the center of curvature and the last Ray is Ray passing through pole so guys if I pass any rate through pole what will happen if I pass any Ray this is pole this is focus this is Center of curvature if I pass any rate through pole what will happen if will it will be reflected accordingly it's called oblique incidence it's called oblique incidence what do we call it guys

42:27 oblique incidence so any Ray passing through the pole will reflect at the same angle so these are the three rays that you will be considering okay clear but what about the convex mirror guys let me tell you if you take con Vex mirror I will be telling in the same diagram this is pole this is F this is C the first is if you take any Ray parallel to the principal axis it won't go like this obviously it's a mirror it will reflect so it will reflect it in such a way that it will be appeared to coming from Focus so this is the case here second Ray is if you pass any Ray through pole same nature is observed next is any Ray passing through Center

43:12 of curvature the ray is incident on Center of curvature it will retrace its path because it the ray the all the parameters are behind the mirror clear so this is the case for convex mirror let me tell you this is the case for convex mirror okay clear guys this was the case for concave mirror clear okay draw this so keeping this in mind now we'll be studying the image formation down on main part of this chapter is you know is going about to start cases of image formation by concave mirror so guys before starting with the cases let me tell you three terms first is for every

44:00 image we will be considering the image size how is the image whether it is same size Right image can be of same size image can be enlarged it can be larger than the object or image can be diminished it can be smaller than the object let me tell you so for every case we have to consider these terms second is whether the image is real or virtual real means raise meeting in actual virtual means the race appear to meet we have to consider this thing third is image and object distance so we have to consider these three

44:46 parameters for every ray diagram imagine object distance clear guys okay so we will be drawing each and every ray diagram see that why I am doing why am I uh I'm about to do that because I want you to draw the diagram by yourself it's not like I I would have you know I would have a brought some pasted pictures of hair in of the ray diagram but I I don't consider doing doing that because I want you to dot the diagram the way I am about to draw is it clear okay so these are the three points you should be considering so case number first case number first draw concave mirror like this okay this is pole Mark all the

45:32 parameters right so guys First We Take object at Infinity the I will be showing the object by arrow and image also by Arrow so guys if I take object at Infinity the Rays comes parallel this is the thing right so obviously they will meet at the focus so where is the image formed at Focus so I denote object at Infinity I will be writing this in short I means image image add Focus Right image at focus and how is the size the image is point size highly diminished it is called very very small or I can call it image size is point size

46:17 images Point size right and whether it is real or virtual guys this is real image because rays are actually meeting you don't have to extend them and they are formed in front of mirror so image is real and inverted clear so the this is how we are going to write every parameter clear guys okay next case next case is sorry next case guys draw the concave mirror project on camera this is pole this is Focus Center of curvature brought the object closer to the mirror now this is the object guys this is the object guys

47:04 so first is Ray parallel to principle axis it might pass through Focus second relay is rate incident on the pole so guys this the here the ray will meeting like this wait yeah sorry my bad here the Ray will be meeting like this clear this is the first case right second is here the Rays will be meeting like this this is the second case so guys this is image so this is object this is image because this is where reflected rays are meeting so this is object this is image so object is is we write it Beyond C Beyond Center of

47:50 curvature image between f and c between focus and center of curvature image is whether it is it whether it is enlarged of same size or diminished this is small object is bigger than the image so guys image is diminished Right image is diminished is it clear image is diminished and whether it is real obviously it is real because rays are actually meeting so it is real and inverted clear okay third case third case guys just draw it by with me what could be the third guess bring object now more closer to the Mirror

48:37 this is pole this is focus this is Center of curvature now object will lie on Center of curvature what will happen first way again parallel to principal axis it will meet here okay second Ray is oblique incidence it will meet here so guys as you can see object and image are just up on each other here okay so where is object at C where is image at C and object the image here is of same size guys here the image is of same size right here image is off same size and whether it is real obviously the rays are actually meeting

49:22 if you place a screen here guys you will get image on this screen okay so here the image is real and inverted is it clear real and inverted okay clear guys just recall all the cases now object will become more closer to the mirror right fourth case what will happen fourth case guys principle X says poll Focus Center of curvature and this is our object more closer to mirror again same rays will be taken right and here again the Rays will meet like this okay my bad uh let me draw

50:09 this again okay so here the Rays will be meeting like this right here also so basically this is our image formed this is our image formed and this is our object clear okay guys so you can see here this is the object and this is the image this is the object and this is the image what about the parameters here can you tell me what about the parameters object is what between C and F right what about the image image is beyond C right whether image is enlarge yes here

50:54 image is bigger than the object right so you can see enlarge images enlarge image whether it is real obviously yes image is real and inverted clear images real and inverted second last case fifth one second last case let me draw both the mirrors here and this is this will be our sixth case clear guys this is pole this is focus this is Center of curvature okay this is pole this is focus this is Center of curvature okay guys clear now object

51:40 will be at focus more closer to the mirror so guys here the ray will become like this parallel and oblique instance now guys you can see these rays are not meeting in actual these are parallel rays so what will you write object add Focus so guys what we assume that image are meeting at the infinity at very large distance parallel rays mid Edge at Infinity okay so image at Infinity size is highly enlarged image will be very very enlarged highly and large and obviously the rate will meet in actual we we see that so the size nature will be real and inverted

52:27 clear okay now more closer to the mirror again this is the last case you cannot keep the object Beyond I mean after this obviously so between F and C what will happen guys first is let me take Ray normal to the Mirror like this so it will up it appears to pass through let me redraw this again so basically here you take you have taken object like this so if you consider normal incidence the ray will appear to pass through C now if you pass any rate through this pole it will go like this so if you back extend these Rays guys what will happen they won't meet here like I had told you in the

53:13 plane mirror they won't meet here but if you back extend them they appear to meet here so guys here the case is different where is object where is object between F and P where is image guys here image is behind the mirror because it's virtual here the image is behind the mirror is it clear is it clear guys what about the nature or what about the size obviously it is bigger than the object this image is bigger right so it is enlarged it is enlarged clear and what about the nature it is virtual and erect it is

53:58 virtual and erect clear it is virtual and erect size erect and virtual okay clear so Guys these were the cases formed by the concave mirror now what about the convex mirror guys convex mirror has only two cases if I talk about convex mirror guys right so basically convex mirror has only two cases this is case one and here we will be considering its case 2 right so basically this is pole this is focus this is Center of curvature okay let us draw the another concave convex mirror this is pole this is focus

54:46 this is Center of curvature now here the nature is different guys concave mirror was converging but convex mirror is diverging it is diverging mirror what will happen if you consider the Rays it will diverse them like they appear to to be coming from F right it will diverse them clear guys so here what is where is the object first case is same object at Infinity where is image image add focus and it is point size it is Point size and what is the next thing it is virtual or real raise are not meeting

55:31 in actual guys so this is known as the virtual image clear this is virtual and erect virtual and erect clear now bring object closer to the mirror so again same race parallel they will appear to be coming from focus and then passing through p and they will go like this now these Rays won't meet in actual but if you back extend them they appear to come from here so is this is the object and this is the image guys this is the object this is the image so here also where is object object is anywhere if you place the object anywhere between pole and infinity

56:18 object is between Infinity and Pole where is the image formed image will be found between p and F between P and F guys between pole and focus what about the size or what about the nature obviously it is also virtual it is also virtual erect and it is diminished it is diminished clearer is it clear to you okay so these were the cases guide of the spherical mirror so what you can conclude that image found by concave mirror has a variety and large feminist same size but con wax mirror can only form diminished image and virtual image

57:05 so it has its restriction and its own application because because of this or based on this clear okay fine let's do a question for a recall question is array of light is passing through the principal Focus after Reflection from the mirror what will happen guys if you pass any rate through principal Focus can you recall it any row any Ray through principle Focus guys what will happen to the ray what will happen to the ray if you if it passes through Focus guys I had just told you it will it will what any Ray passing through the principal Focus will become parallel to principal axis I have told you whether

57:51 it is concave or convex it will become parallel to the principal axis so which option is correct a become parallel to the principal axis very very simple question just for a recall clear okay convex mirror cases are done okay I had told you the cases of image formed by a convex mirror so this is already done okay now applications how do how we use these spherical minutes because see I had told you we had a different variety of images concave mirror can form all but basically both type of images it can form real image it can also form virtual image it can form a large image it can form same size image it can form

58:38 diminished image while convex mirror has some restrictions it can only form virtual erect image and diminished image so guys based on this image formation we have a variety so guys have you seen when a dentist is performing some treatment he uses some kind of mirror here so basically you can see the image is zoomed the image is zoomed or I can see it is magnified so guys what type of mirror it could be obviously concave mirror it can't be convex it cannot magnify that it cannot enlarge the image it cannot form a large image so this is convex concave mirror used by the dentist right next is mirror in our headlight of the vehicle so guys

59:24 this this we have concave mirror in the headlight of the vehicle why is that why is that guys see basically what do we want in our headlight we want the range to be maximum we want a parallel beam of light we want the beam to be parallel so we can it can go farther away so guys what can we do basically if or any Ray basically what we do is we place the bulb can you see this bulb this bulb is placed at the focus here so guys when the Rays will appear will emerge from this they will become parallel to principle axisner because the bulb is placed around Focus so we get a parallel beam of light

1:00:11 we get a parallel beam of light a parallel beam of light is it clear guys similarly in this antennas in this antennas also the rays are the this receiver is kept at the focus basically so signals coming parallel will merge here so it's a con it's concave shift clear guys that's this is the application these are the applications of the concave mirror okay next is concavex so guys I had told you in the beginning that you can get the view of this complete field in this

1:00:56 small mirror that means it is forming diminished image so diminished and virtual erect image is found by convex so basically we get a wide field of view we got we get a wide field of view wide field off view clear similarly in the rear view mirror of our vehicles it has convex mirror rear view mirrors in the vehicles it has convex mirror to get a wild field of view we can see the complete traffic because of this convex mirror clear guys

1:01:42 okay now next is sign convention what is sign convention guys see basically we had seen how do we form the image how object distance is seen how image distance is seen But guy if I ask you how can you calculate the object distance are there any calculations obviously yes there is a calculation for focal length there is a calculation for object distance for image distance all these things have some calculations so basically before moving into that formula we should be knowing sine convention so guys what is the sign convention see we have three parameters one is image distance other is object distance

1:02:30 other is object distance third is focal length or radius of curvature focal length or radius of curvature so Guys these three things have some sign how if I take any mirror now listen to me very very carefully if I take any mirror the pole of the mirror is taken as the origin the pole of the mirror is taken as the origin origin of what origin of cart is in plane can you recall it guys origin of Cartesian plane this is origin so right hand side we have positive x-axis left hand side we have negative x axis

1:03:16 upperward we have positive y-axis downward we had negative Y axis same cases here distance to the left of pole are negative distance to the left of polar negative distance to the right of polar positive distance upwards are taken as positive for example object I always keep the object like this so object height is positive if distance is downwards it is negative same to the Cartesian plane no need to remember same as Cartesian plane the X Y plane clear right also we have you can write one more thing also we have image and object

1:04:03 height image and object height is it clear guys okay writing down this is very very important thing you should be knowing guys okay these are the various parameters now keeping this thing in mind we have two formulas one is the mirror formula that relays the image distance V is the image distance let me write it down V is the image distance guys and U is the object distance U is the object distance and what is f guys f is the

1:04:48 focal length f is the focal length clear okay guys so what is mirror Formula 1 by f is equals to 1 by V plus 1 by U this is the mirror formula that relays these three parameters now we have formula for magnification this m is the magnification it is ratio of image height to the object height image height is H dash object height is H so MH H dash upon H or it is also equal to minus V by U this minus is present in the formula this minus is present in the formula so Guys these are the two formulas you should be knowing to calculate any parameter that you want related to the image formed by spherical

1:05:35 mirror now question is Sir how can we put the values here so guys there is a note for you note is write it down put all parameters notice put all parameters with sign here just put all parameters with sign light f u v image height object height you have to put all the parameter with sign how whether it is positive it is negative positive negative just look at the figure look at remember recall all the cases I have just told you and just put all the parameters with sign is it clear guys okay now let me tell you how

1:06:22 to take the science it is very very important guys thing is we have magnification we have image distance we have object distance we have focal length we have image height we have object height now question is Sir how to recall the all the sign convention so guys how can you do this C basically I had told you about concave mirror I had told you about concave mirror and convex mirror and convex mirror so guys what are the various parameter I am going to tell you basically we have object distance image distance focal length image height object height okay guys now listen to me very very carefully no need to remember

1:07:07 this just listen to me concave object is always placed to the left so object distance is always negative it is always placed to the left hand side this is the first sign convention image concave mirror can form image can you recall I had just told you it can form image both on the left hand side and the right hand side guys we call it just recall it I had told you concave mirror can you see here image is formed on the left so V is negative here image is also formed on the left so V is negative but here it is formed on the right so guys here V is positive clear but what about the object in all

1:07:54 the cases guys object is placed to the left that means object distance is negative in each of the case can you are you getting it now object distance is negative for each of the case clear right so image distance can be positive and negative for concave mirror but what about convex guys what about convex can you recall it guys convex mirror always form the image to the right so that's why four convex Mirror Image distance is always positive image distance is always positive clear okay

1:08:40 done so image distance is always positive focal length guys so guys focal length of concave mirror is negative as I told you it lies to the left for convex is is positive image height see concave mirror can form the image upwards as well as downwards so image height for concave mirror can be both positive or negative depending on the object distance it or a but corn convex mirror is always forms virtual and erect image that's why it is image height is positive upwards right object height is positive for all we never Place object inverted clear guys so this is the sign convention you should be following okay just write it down briefly guys without this you won't be

1:09:27 able to solve the numericals very very clearly clear guys okay now next parameter is magnification what about the magnification guys how can you find the magnification so guys basically magnification can be of two types right it can be positive it can be negative okay if magnification is positive guys so image is virtual and erect just recall this guys if magnification is positive image will be virtual and erect but if it is negative image will be real and

1:10:14 inverted how's the image guys it is real and inverted clear so Guys these are the two things that you should be considering these are the two things that you should be considering about the sign convention this is very very important slide out of all the slides we have read till now okay clear guys should I move forward now let's do a numerical try this try this question is a concave mirror produces three times three times magnified image enlarge obviously real image the image is real okay

1:11:01 and of an object placed at 10 centimeter in front of it object is placed at 10 centimeter and image is form produced three times and large and it is real you have to find the image distance try it pause and try it I am about to tell you the solution see you guys basically magnification is what it is three but since the image is real it is -3 I told you take with sign what is magnification it is minus V by U okay so guys from here minus V is equals to minus 3 U cross multiply it so from here V is equals to 3u okay

1:11:47 now what is the object distance it is 10 centimeter so guys object distance is 10 centimeter but this is not right because take it negative I had told you always take the object distance as negative is it clear so object distance is negative now put the value here what is the image distance guys V is 3 into minus 10 so minus 30 centimeter this is the image distance V minus 30 centimeter okay so in the options you have to tile the magnitude only not the sign so a option is correct it would have been minus 30 right then that that option also would have also been correct clear

1:12:33 okay so guys this is how you take the sign convention or sine of V sine of U sine of f right sine of object distance image height object height all the signs should be taken into consideration very very clearly okay should I move forward now clear okay now next part is refraction of light what is refraction of light so guys have you seen uh phenomena's like this for example while a pencil is bending into the water it appears that the pencil is broken but it is not broken it appears to you like it is broken so this is due to refraction of light or you can see the arrow is inverted it is to the right but it appears to you to the left

1:13:18 if you look at the arrow through a glass full of water so why has this happened due to refraction of light here also you can see the pattern of the pattern appears to be changed the pattern is different while looking through the water so this is also due to refraction of light so diffraction means The Binding of ray of light when light enters from one medium to another it bends it paths changes that is when light Ray is going from air to water basically it should go like this but it has Bend so this bending is due to change in medium while a light is going from air to water so this is known as the refraction of light so what is refraction when light travels obliquely

1:14:06 obliquely means at a certain angle obliquely means at a certain angle when light is traveling obliquely from one medium to another the direction of propagation of the light in the second medium changes this you can see the direction has changed now it is not going straight it has Bent by certain amount so this change in direction is known as the refraction of light light rays refracts when the Whenever there is a change in medium so in reflection we did not have a change in medium here we have a change in medium is it clear okay so the path the path of the light Ray changes or you can also call like the direction of the

1:14:52 light Ray changes in case of the reflection of light clear guys okay now how does light Ray is refracted by while passing through the glass slab see guys basically what happens is air is a rarer medium right it has lesser density glass is comparatively denser medium guys so guys whenever light ray goes from Air to glass from rarer to denser you can see this is the normal Ray at the point of incidence the light Ray has bent towards the normal due to going from denser to medium but at the second point it is going from denser to rarer so it has bent away from normal

1:15:37 okay so guys this is the final Ray this is the incident Ray this is the incident Ray this is the refracted Ray this is the refracted Ray and this is the emergency this is the I'm urgent Ray okay guys is it clear to you so guys what do You observe if there were no glass slab this Ray would have gone straight but due to presence of this the Ray has been displaced by some distance to the left and this displacement is called lateral displacement literally displaced

1:16:24 due to Glass slab there is a formula for that but you will study this in the you know higher classes so this is called lateral displacement and one more thing what about the angles guys this is angle of incidence this is angle of refraction this is angle of refraction right and this e known as angle of emergence so e is called angle of emergence angle of emergence the angle found by the emergent Ray with the normal so this is called angle of emergence or I is known as the angle of incidence I is known as the angle of incidence is it clear guys okay so basically guys I had told you light Ray bands this what we this we had

1:17:10 seen But thing is how does it Bend and why does it Bend this is a more important question why does light Ray bends fight going from one medium to another this is the question so guys this the answer to this question is refractive index what is refractive index C basically when light goes from one medium to another okay guys right this is the angle of incidence this is angle of refraction the speed of light in this medium is V2 here it is V V1 here it is V2 because this is medium one let's say this is medium one and guys this is medium two so here speed of light is V1 here speed

1:17:56 of light is V2 let's say the refractive indexer of this medium is N1 this medium is N2 so guys refractive index is a parameter that tells us how much will the light Ray Bend and how much will the light how will be the how much will be the speed of the light Ray in that Medium because rice light Ray does not travel with the same speed in air in glass in water the speed of light is different in different mediums and why is that this is because of the refractive index clear okay so what is refractive index guys just recall this formula N1 by N2 is equals to V2 by V1 this is the formula you should remember okay this is the formula you should remember but what about if the first

1:18:42 medium is air if first medium is here so guys N1 will be equal to 1 because the refractive index of air is one it does not bend the light Ray and what is the speed of light in air it is equals to small C which is 3 into 10 raised to the Power 8 meter per second okay so guys if I put this in this Formula 1 upon N2 this week will be equal to V2 upon C so guys from here what is N2 it is C by V2 or in journal we write n is equals to C by v v is the speed of light in the respective medium so what is that if this refractive index guys refractive index n is the mean of a medium is the ratio of velocity of light

1:19:30 in vacuum which is C to the velocity of light in the respective medium which is V so and so n is equals to C by V n is equals to C by v c is the speed of light in vacuum and V is the speed of light in that respective medium which you are talking about right so guys you can see refractive index is inversely

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