based on light distance which is actually based on light

 based on light distance which is actually based on light
 based on light distance which is actually based on light

So dear strains now it is time to start this very important and very interesting chapter of physics which is actually based on light distance which is actually based on light we have also seen some other chapters which are based on light non strains the name of this chapter that we are going to study now is the human eye and the colourful world the human eye and the colourful world is friends so strange maybe you are able to guess that we are going to study this chapter in two parts in part 1 we are going to study about the human eye and in part 2 we are going to study about the colourful world okay so it's.

 So you can understand how important this chapter is right friends please understand I is very important for us with eye we see the entire world streets so this is a very important chapters friends okay so let us start this chapter and let us start studying about human eye right this one are you ready so let's set go this is the human eye if we take out the human eye from inside the body it will look like this streets it will look like this it will look like a small ball streets that's why it is called an eye ball that's why it is called an eye ball strengths and eye ball okay so you can see our eyes actually spherical in shape it's very curl in shape right distance and its diameter and its diameter this is its diameter strange.

 That is approximately 2.3 centimeter okay however in some human beings it can be slightly more or slightly less range now what we want to do here is to insist that we want to go inside the eye inside this eyeball and see what is the structure inside it strains so strains now we'll study structure of eye structure of eye so this is our eye from outside as we see it every day but from inside the eye is like this and there are lot of things inside it as you can see so strains first of all look at this look at this this structure here this structure here is called this structure here is called cornea students cornea it is basically like a transparent.

 Membrane transparent membrane it is basically like a transparent membrane equations so if you look at AI from outside there is a transparent membrane on I there is a transparent membrane on I right so that is this thing actually that is cornea it's a transparent membrane what is its job students see it protects our eyes it protects our eyes due to presence of this cornea dust particles cannot go inside our eyes or a small small particles cannot go inside our eyes if this cornea will not be there they can go inside our eyes and harm us okay so it protects protects eye from dust particles from dust particles okay so it's and as you can see strains it is.

 Curved this cornea is curved in shape it is convex shaped convex shaped right joints so this is cornea transparent membrane in the front of eye then I students look at this structure this is a structure of muscle students this structure here is called iris is called iris you can also see this structure here strains now in the mid of iris there is a whole strength that is actually called pupil it is very important strains as we will see later in this chapter if we look at ice trends from outside this black structure here is actually pupil is pupil and this green and structure here strengths is actually iris is actually Irish strains as we will see later in this.

 Chapter that light enters our eyes light enters our eyes and that is through this pupil only let so light will come inside our eye through this pupil so we can write this down here in short that light Inter's I threw it through pupil basically okay now let us talk a bit about this iris instance this iris is actually ring shaped ring shaped as you can see here it's like a ring it's like a ring with a hole at the center it is like a ring with a hole in the center streets and also it is color distance it is colored as you can see here it is looking greenish.

 So it is color distance and the interesting thing is trains is that in different human beings color of Irish may vary color of Irish may vary let me show you this photograph strains see here or see here first trends you can see the color of Irish here okay it is greenish in this case you can see the color farish's clarify regions what do you think brownish right in this case you can see the curve Irish is it is different is different somewhat bluish right so strange color of Irish can vary in different different human beings you can do a small exercise students look deeply into the eyes of different people around you okay and you will notice that color of Irish is different in all of them slightly different in all of them strains okay.

 So so do this exercise you will have fun in strains then look at this structure this a structure this is the most important thing in your eyes trains this is actually a lens strength this is actually a lens okay and as you can see from the shape as you can see from the shape it is a it is a which type of lens which type of lenses their strengths look at the shape look at the shape I am sure strengths you are able to understand that it is actually a convex lens it is actually a convex lens focus once so it is a convex lens so in strains very importantly inside your eye there is a convex lens inside your eye there is a convex lens known strains you might be thinking that lenses are generally made of glass lenses are generally made up of glass strands right.

 So is this lens also made up of clocks definitely noise friends definitely know the lens inside your eye is not made of glass it is made above a jelly like a jelly like transparent substantial a jelly like transparent substance August prints obviously it cannot be made up of glass right if glass will be there inside your eyes your eyes will be damaged students right so this lens is made above a jelly light transparent subset substantial okay now look at this structure students this thing here that is called suspensory ligaments suspensory ligaments while ligaments strains because this structure is to win number you can see here as well this is.

 Also suspensory ligament assurance right so these two are suspensory ligaments now what are the doing strains you can clearly see that this and this these two suspensory ligaments are holding this lens at its place so what are they doing they are holding lens they are holding lens at its place at its place they're holding lens at its place okay so this is a suspensory ligament this is another suspensory ligament Astrid's okay now look at this structure strength this is a muscular structure and this is called ciliary muscles ciliary muscles once again this is also ciliary muscles as friends fine we'll see in we'll see about ciliary muscles in great detail in this chapter actually because this is very important this ciliary muscles are actually.

 Very important okay now look at this structure here in this wall like structure at the back of eye at the back of I is again a very important part of eye and this is called retina this is called retina okay now you can see this is a nervous student right so this is called optical nerves this is called optical nerves optical nerves this goes to brain this goes to brain okay so what is its role that also we will see stones then you can see a point here a point here on retina a point here on retina this point here on retina in front of optical nerves is called blind spot it is called blind spot red Swinson so these are the major parts of eye then this whole structure since this whole structure here this is filled with a liquid that is called whit resume.

 ER that is called vitreous humor witless humor is it it is a transparent liquid it is a transparent liquid okay whit Russ humor you have to remember this name similarly strains in this portion in this portion in this small portion there is another liquid that is called AK was humorous that is called aqueous humor it is also a transparent liquid distance it is also a transparent liquid okay so it's friends why these liquids are transparent why these two liquids are transparent which means we will see later on in this chapter that light rays will travel inside the light rays will travel inside the eye so light rays can travel live these things are transparent right if these things are not transparent how will light travel inside I right so fine strands.

 This was all about the structure of eye now we need to see that how this helps us in looking at the objects in seeing the objects right so strengths that will be studied under the heading working of I working of I so see strains how this works how this I works so suppose there is an object in front of our eye right that may be any object for example we have taken a tree so it strange this is an object in front of our eye this is an object in front of our eye okay now see light rays starting from this object light rays starting from this.

 Object will come and hit our eyes will come and hit our eyes right difference so you can see so in this cornea range which is actually transparent and then this is lens this is lens which is actually a very important thing regiments so what happens this light rays come and hit the cornea they can pass the cornea as it is transparent and then they hit the lens then they hit the lens systems now what happens then this is a lens strengths this is a convex lens actually so this lens will bend the Rays will bend the reason and the reader.

 Actually meeting here when the Rays are actually meeting here on retina on retina screens right so once again I repeat what's going on here light rays start from this object they come and hit the lens lens is going to bend these light rays and these light rays are actually going to be that rating actually going to meet at rating so strains and image is going to be formed on the retina and image is going to be formed on retina so this is basically an image this is basically an image straight straight so here retina is acting as a screen retina is acting as a screen where image is being formed where image is being formed right shoots.

 So strains one thing is important here we have studied about convex lenses right and I highly recommend that you revise convex lenses before we go ahead if you remember convex lenses very well then it's okay otherwise you should revise because knowledge of convex lens is going to be very important in understanding the functioning of eye right turns because the most important part of eye is this convex lens okay.

 So this is an object in front of this convex lens and this convex lens is forming its image on the retina it's forming its image on retina normal students tell me this image this image is real or virtual is it real or is it virtual what do you think is friends but do you think this is a real image or virtually magicians this is clearly a real image this is clearly a real image why Sir it's because you can see the light rays are actually meeting here the light rays are actually meeting here right right is are actually meeting here so it is actually a real image and the and the image is inverted inverted as I've drawn here this image is inverted non-students once again if you remember.

 Convex lensses there we have studied very clearly that when convex lens when convex lenss forms and real image forms a real image it is always inverted we have studied that when a convex lens forms a real image it is always inverted so the image formed here is inverted so friends we can write this down whatever we have studied till now so it means light rays from object hit our eyes lens forms the image of object image of object on retina as we have seen the image is real and inverted right difference now.

 See what happens next what happens next now look at this students these are optical nerves these are optical nerves right friends and where these optical nerves go where these optical nerves go so as I have told you they go to brain instruments they go to brain okay so when there is an object in front of our eyes it's image is formed on retina by the lens and then this optical nerves these optical nerves take the information of this image take the information of this image to our brain to our brain okay so when this image is formed these optical nerves become active they take the information of this image to our brain so our brain is able to process this information and that's how we feel that okay there is an object in front of us there is an.

 Object in front of us okay so let me write this down optical nerves take the information of image to the brain as I told you brain processes the information and we feel the presence of the object you understand so that is how I basically works this is something very basic we'll see the entire working in more detail also but this is a basic working stress that there is an object light rays from that object hit the lens lens will form an image on retina then this optical nose will take this information to the brain then brain can do you know lot of things and due to which we feel that okay there is an object in front of us and we see the object.

 Okay now here strains you may be having one small doubt students please notice that the image here is inverted image here is inverted right so strengths if we are looking at a tree the image formed in our eye is inverted so so what should happen so strands we should see an inverted tree we should see an inverted tree a tree upside down right because image formed in our eye is inverted but friends you know that that is not something that happens in our day to day life you know our day to day life if we look at a tree we will see it erect we will see it right so what is going on here what is going on here you understand what is going on here if the emails here is inverted in our eye how are we able to see an erect object how are we able to see any rect object in our day-to-day life which friends see our brain is actually very smart brain is.

 Very smart right when this image is formed the information of this image goes to the brain goes to the brain right and inside the brain inside the brain this image this image is further inverted inside the brain this image is further inverted we can write the song inside the brain image is further inverted image is further inverted so what will happen now inside the brain this image will further inverted and if it is further inverted it will become it it will become erect it will become erect and we will see an erect object right distance.

 So so you are getting the point fine okay so this is the basic working of ice trends and I also must tell you one more thing here one more thing here that this basic working of why this basic working of I is very similar to camera basic working of working of AI is similar to camera is similar to camera strengths you know water camera right so if you have ever studied about cameras earlier you will know that cameras also work pretty much in the same manner pretty much in the same manner you may not need to see this point in great detail you just need to know this fact right that camera also works very much like this right.

 So let us move ahead Oh constraints now role of iris and pupil so strengths first of all tell me where is iris variance pupil in this diagram tell me we have studied that where is Irish trends I am sure you are able to think this is actually Irish right distance and even this is address this is iris right and what about pupil this whole hair is strange this whole here is pupil is pupil right distance now I am going to show you a very interesting photograph look at the strengths look at this look at these two different eyes do you notice any difference trends you notice any difference look carefully stones I am sure students you can look at you can find the difference here this is pupil this black portion is pupil right this black portion is pupil right.

 So here the pupil is small so here we have a small pupil small pupil and here is friends we have large pupil large pupil right so strains sometimes our eyes is like this and at other times our eyes is like this then we are actually sitting at a very bright place at a very bright place at a very bright place where there is lot of light there's lot of light our eyes is actually like this and we are when we are actually sitting at a dim place maybe in a dark room where there is very little light maybe in a cinema hall where there is very little light.

 Strains then our eyes is like this when then our eyes are like this you understand if we are sitting at a very bright place maybe outside you know maybe outside on a very sunny day or in a room where there are a lot of lights our eyes is like this it mean pupil is small but if you are at a dark place maybe at night or in a cinema hall our Isis like this means the pupil is large so what is going on here is prints that is what we need to understand I will explain you instance see if there is an object in front of us light rays starting on the object comes and enters the eye comes and enters the eyes right light rays will start on the object and they.

 Will come inside the eye like this so they are coming inside the eye through pupil they are coming inside the eye through pupil writes prints so see what happens that if we are sitting in bright light if we are sitting in bright light there is a problem why there is a problem that if there is lot of light inside outside if there is lot of light outside lot of light through this pupil can come inside the eye right if there is bright light outside lot of light rays can come inside our I can come inside our eye through this pupil now that is not safe for the eye if large amount of light comes inside the eye may be damaged the eye may.

 Be damaged so strengths let me write this down that I may be damaged I may be damaged if large amount of light enters focus once if a large amount of light enters I I may be damaged so strains you understand the point now that if we are sitting in bright light if we are sitting in bright light we need a smaller pupil we need a small pupil if this pupil will be small only a small amount of light will enter and our I will be safe and our I will be safe so in bright light in bright light pupil should be small pupil should be small that's why strange we have a small pupil when we are in bright light right now what happens when we are in dim light sequence if we are in dim light there is very little out light outside there's very little light outside.

 This very little light outside then it strains then strains we want a lot of light to come inside because there is very little light outside so lot of light has to come inside so that a clear image is formed there so that a clear image is formed here isn't a difference so if the pupil is big now if the pupil is big now if the pupil is big now large amount of light can come and a clearer image will be formed you understand so in dim light M dim light large pupil is needed large pupil is needed so that good amount of light can come inside good amount of light can come inside and a clear image and a clear image is formed on retina is formed on retina.

 So Ashwin I am sure now you understand why we have a small pupil in bright light and why we have large pupil in dim light right Swinson I can repeat it briefly if you want that in bright light in bright light this lot of light this lot of light outside if lot of light enters our eyes then our eyes will be damaged our eyes will be damaged right so we need a small peepee so we need a small pupil so that only small amount of light can come inside and I see when we are in dim light strains when we are in dim light this very little light so this will little light outside so a large pupil is needed so a large pupil is needed to gather a lot of light to gather a lot of light so that the image formed here is clear clear and we can see the object you understand.

 No strange what it means is that if you are sitting in a bright room your eyes like this right when you are sitting in a dim room your eyes like this registrants so it means that your eye is automatically changing your eyes automatically changing when you are sifting from bright to dim or dim to bright room right right difference so if you are shifting from applied to dim room or dim to bright room the size of pupil the size of pupil automatically changes you don't even know about the distance right did you know about this before.

 No so since childhood since you have been born students this phenomena is continuously happening whenever you are changing whenever you are going to bright light your eye is becoming like this whenever you are going to dim light or in a dim room or in a dark room your eyes becoming like this and automatically the size of pupil is changing so in how is this happening how is this happening how is this phenomena happening automatically so that is what we need to understand strains so here iris plays a very important role iris plays a very important role leave what happens to ends when you are in bright light and also when you are in dim light I will tell you both the cases when you are in bright lights friends this iris this iris.

Will expand like this this address will expand like this right when you are in a bright room when you are in a bright room this iris this address will expand iris will expand so if the RS expands pupil will become spawned you can understand right so when you are in bright room this iris is actually expanding making the pupil small locations so in bright room when you are in bright light iris expands making pupil small making pupil looks small occasions and what happens when you go to a dim room or dim light this.

 RS strengths this iris strains moves like this contracts this iris contracts making the pupil larger the iris contracts the iris contracts making the pupil larger iris contracts making pupil larger okay so I am sure strengths you are able to understand the phenomena and you are able to understand that this iris is actually a very important thing in our eyes right this RS can actually contract or expand contract and expand to control the size of pupil to control the size of pupil so we can even write down that iris expands or contracts or contracts to control size of pupil

 Okay to control size of pupil so which means I hope you have understood the concept here right and please understand that this is happening all the time strains is happening all the time with your eyes right the size of pupil is always changing when you are in bright light and when you are in dim light restraints let us do some more examples here strains which will help you to understand this concept even better

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