THE HUMAN EYE & THE COLOURFUL WORLD | PART-2 (SCIENCE - PHYSICS) GRADE-10TH CBSE BOARD 2026-27

[00:00:10]Rabbit planning for >> today. Sel, what happened to Selam?

[00:00:18]He's hyperactive today.

[00:00:21]Huh?

[00:00:23]>> No, no, no. After this, Max I will do maths morning or evening but session >> I will solve it better after class.

[00:00:48]>> I started the session.

[00:00:58]Everyone join first please. Now look here last class in human colorful world.

[00:01:06]>> No see listen one thing is there now.

[00:01:09]See please understand one thing. Can I start? See you asked me many questions.

[00:01:15]Now in that one of the question was why uh tears are salt salty. Now you understood aquasumer is the responsible part because it is saline and the liquid will be coming every time when you are shutter it off like primal glands are giving what the things which are the enzymes which is actually fighting with the different type of bacterias and virus keeping you your eyes safe but many times conjectivities or any different type of good evening everyone please kindly join today uh this is 40 minutes class after 40 minutes class I will see if I'm not tired means another 20 minutes class I will keep for maths no online complete online you will go home from home you will join no now then morning 6:00 maths >> deal everybody morning 6:00 maths >> yes hers we previous 40 minute session you did not join please check that 40-minut session very important content we have discussed >> huh Can I start please see listen we have talked about hey zeram hers present everybody yes 6:00 morning I'm keeping the class tomorrow there's no holiday children listen now August you are having two sample exam paper exams for math and two sample paper exams for science correction will not be done by me it will be done from side everything will be totally technical coming. Yes, I will also do because I have cross questions we have to check. Rohit, thank you for joining the session. Everybody please listen. We discussed about human eye. We talked about the shape of the human eye. What was the shape?

[00:03:07]Spherical. Understood? After that we discussed about sclerids. Scarits are the white portion of the human eye. So one by one just small content we will discuss aquas humor and bitress humor also we discussed.

[00:03:24]Yes we discussed all the parts please listen one short review preview sorry.

[00:03:30]So now look here we had discussion about scarits. The white portion of the human eye is called as sclerits. So if you will see this white coating it is exactly called as sclerits. Understood?

[00:03:43]This is suspensary ligament and this is celiary muscles. This is lens. Lens is made with >> convex lens made with protein. Yes, double convex and it is made with protein and its most important part is it can change its focal length. The human made sophisticated cameras they can't change their focal length but our human eye the convex lens can change their focal length. That makes it very very unique. Remember this? So the focal length of where convex lens of human eye can change. Understood? Please convergence also change because of change in focal length convergence. So that only you can see nearby object and far of object. Understood?

[00:04:32]Now we talked about one thing just slide. This is filled with aqua humor.

[00:04:39]White is jelly like substance. This is filled with vitrus humor that is gray substance. Understood? And why this fluid is present inside? This fluid is giving posture to the eye. That time if air pressure or at the time of atmospheric pressure now the shape of the eyeball cannot change. You know one thing very very important children please listen this. I'm telling you technicalities like when you will go deep down earth like in water. So divers of swimmers are there. Now the more they will start going down the more they will start feeling the pressure atmospheric the water pressure will generate at that time now the not only the eyeball the full body cells they will be exactly in pressure got it so eyeball if the split will not be present there what will happen they will shrink the change in shape will be there that's not good I I hope you might have understood so what is filled inside beta vrus human it is giving shape. I hope you people have understood gray is color so that the light cannot split. Understood? The light can directly go after reflection and refraction. So a refraction means it is going from one medium to another medium. So refraction is occurring from cornea. Most of the light ray will deviate. Some light ray will enter and focus and then it will fall into retina.

[00:06:03]So this was the thing we have studied.

[00:06:07]Now sclerotic region is the region whitish region is called as sclerotic.

[00:06:12]Now we talked about cornea. Cornea is called as window to the world. The bulging section which allow light to come inside. Next part was vitrus humor and we discussed yes jelly like fluid.

[00:06:25]It will keep the shape intact. Next part we have studied and that was aquas humor. The front part is aquas humor.

[00:06:34]And we learned one thing. Every wing when we are doing wing little bit of aqua humor is coming out from the eyes and it is exactly helping the eye lens or eye shutter to close and open without friction. Understood not. So vitrus humor is very very important. I hope pineal everybody Monish thank you Monish by with name you are joining Jerom Shanmati pineal thank you for changing your name now it's very easy for them also Rashan thank you so much zer zer is there yes okay Rohit is also there now listen aromera yashwini and yes now rau is there okay so vivink right tiny drop of aquasum flows out of the side of the eye and it washes the eye and keep the cornea moist that's very important but if you will not sleep for long time now the very fine blood vessels are present inside your eyeball now it will become very reddish you you might have seen that it will become very reddish because of pressure only I hope you might have understood because eye needs relaxation and so only now when your eye will be having more of that itchiness than something you you love to close your eyes for some time correct now and you know what one scientific reason behind is every after 8 hours now you will automatically take a small nap small nap means for two to three second sleep will be more supportive more than 5 hours sleep are you understanding yes because now that little bit of jerk and little bit of relaxation now it will be very very helpful and it will be exactly taking out your what do you call all that clips the eye has stored in your brain I hope you might have understood this That's a short cleaning sessions.

[00:08:23]Okay. So now we will talk about iris.

[00:08:26]Iris is just like a shutter. And I discussed one thing like the shutter can be contracted and relaxed. Okay. Come here and explain about Irish.

[00:08:41]>> Yeah. Afternoon timing.

[00:08:47]Please don't waste time. I will be discussing now he will draw.

[00:09:01]See this is exactly the Irish. Now this shutter will become small and it will become expanded. Where it will be expanded beta?

[00:09:14]This is for >> dim bright case. Understood? And this case will be coming for dim light. You need to remember this.

[00:09:27]Why dim means that this part now iris will relax or contract.

[00:09:34]Contract. Iris. This shatter this will contract. Contraction of it will make the hole bigger. In which place? dim light. Understood? And here when bright room will be there, the shutter will relax. The relaxing of shutter will make the pupil size small. I hope now it is a very clear concept everybody. Yes, absolutely correct. That day hers also answered yesterday also he answered this question perfectly. This is the correct answer only. When iris will contract >> in dim room relax, >> right? Understood or not? So this is exactly happening. Absolutely correct children. Now let's go with the content please.

[00:10:22]Bad news is it is getting struck now and break your head.

[00:10:33]Wait no no break. Keep your mouth shut.

[00:10:43]Is it closed?

[00:10:47]>> See, I hope you people have understood.

[00:10:49]After that we talked about what?

[00:10:51]Optical.

[00:10:55]>> Optical or optic nerve?

[00:10:58]>> Optic nerves. Optic nerves are what?

[00:11:04]>> What is black spot?

[00:11:06]Anybody who can answer me. What is black spot?

[00:11:10]>> Yeah. Afternoon only electrical impulses.

[00:11:16]No beta the images will get converted into electrical impulses. Understood?

[00:11:21]Blind spot is the reason from where the optic nerves are going out. So there no image formation is there. There what is not there? Image formation is not there.

[00:11:39]Prince switch it up.

[00:11:45]>> Yes. Is black spot. That is called as blind spot. Black spot. No. Yellow spot is there. Fever. Fever is there.

[00:11:56]Yesi. Blind spot. Absolutely correct.

[00:12:04]Yes. Where the nerves are getting connected. So image formation will not okay online children one very big Maharati is asking how blind is seeing the objects you can only answer how blind can see objects Everyone please listen one very intelligent questions please understand one thing I'm just discussing about it so this we have discussed islands we talked about the island is double convex lens we have learned about it is transparent and flexible tissues it is behind the pubil and it is connected with celiary muscles suspensory ligament and celiary ary muscles. So whenever you will be seeing this part better please understand this is suspensary ligament and celary muscles and celiary muscles contraction and relaxation changes the size of the islands it will become thick or thin. Understood the change of the island size is because of contraction and relaxation of celiary muscles. This is important to know. Now it behind it is called as it is a transparent crystalline structure made up of many concentric layers. Our lens is made with what? Many concentric layers. It is kept in position by a strong elastic frame called as what beta suspensary ligament.

[00:13:50]Our lens is held firm with the help of what bita suspensary ligament. Online children please start answering now just answer this question. Suspensary ligament is connected to celiary muscles and lens is connected to suspensary ligament and suspensary ligament is connected to celiary muscles and celiary muscles are actually taking all their sorts. They are only doing the main work contraction and relaxation. And when they are contracting and relaxing relax they are doing the relaxation they will allow the suspensary ligament to keep on changing the eye lens size. I hope you might have understood. So who is taking doing the most important work? Celiary muscles.

[00:14:39]Celary muscles are directly connected to lens or indirectly.

[00:14:43]That means celary muscles are indirectly connected to >> lens. So it is directly connected to suspensary ligament. What it is called as bit suspensary ligament. What it is called as suspensary ligament.

[00:15:00]I lens bit you need to understand that con student is not understanding what is eye. See our eye lens is convex. By convex why it is called as by double convex lens beta because half half joining together it is make double convex lens. First thing it is made with protein and the protein coated layers are making a shape of convex lens. Now this convex lens now it is not like any type of camera you are taking the camera lens focal length you can't change correct now but here for our eye lens we can change the focal length how the focal length will change when it will be thinner or thicker. So focal length will change because of two things suspensory ligament and celiary muscles. Are you understanding it? So one simple technique I'm teaching you please understand this.

[00:16:04]celiary muscles and this is don't do those things parents are watching you will be in trouble.

[00:16:10]So this is suspensary ligament and this is celiary muscles and this is lens understood. So now what actually happens here beta when the suspense celary muscles will contract what will happen it will allow it to and then it will become thin understood. So thickness or thinness of lens depends upon celiary muscles. Celiary muscles just give a information to suspensory ligament by contracting or relaxing. I hope now you have understood Jerom.

[00:16:46]Yes, I hope now you understood beta. So it's thickness it will become thin or it will become thick. It is totally dependent upon celary muscles. Absolute See it's not only one protein beta the protein this protein is a specific protein and it will be actually made at the time of your birth itself understood when you will be in your mother womb and your body structure will be making that time the maximum of protein quoted will be so when a child is born this protein is already accumulated and made a layer by layer island lens understood or not and this lens this protein will keep on changing that's what So that if I will punch you means you'll understand what type of lens it is there.

[00:17:42]Did you understood everybody? Yes. Do you need to remember this? Like at the time of birth itself children are having eye lens. Correct? Now so at the time of birth itself before birth itself when the full body structure is meeting the most of the protein section. Are you understanding? But the coatings keep on getting converted. And you know what catact is also a type of layer formation. So at old ages now this protein now it will dilate and that time the protein will make it cloudy. Got it?

[00:18:11]As the age is Yes. As the age is proceeding the same protein if it will become cloudy the lens will exactly having that deposition and because of this you can't see the image clearly.

[00:18:22]Sold peoples are having what they're suffering from cataract. I hope now you have understood better. Bala present. I hope everybody understood this concept.

[00:18:34]>> Boyas she is a girl. Yeah.

[00:18:44]Now please remember this section. We have already discussed this part.

[00:18:48]Unwanted things. I don't want everybody see online children they have understood nicely they are discussing it nicely okay now please don't disturb here so the islands help to divide the eye chamber into two parts is dividing anterior and posterior anterior section aquasummer is there posterior section vitrus humor and we will know that one very important information the refractive index of aquas humor is 1.337 and the back chamber between the eye lens and the retina is called as posterior chamber and it is filled with j like material called as vitrus humor and the refractive index of it is also same yes 1.337 so refractive index of aquasumer and vitrus humor is same so refractive index of aquasumer and vitrus humor is same now we will go for celiary muscles I told you celiary muscles plays a very vital role for changing the focal length. You see everybody will anybody will ask the question like what is the main work of celary muscles to see to help you see far off object and nearby object. So celiary muscles will contract and relax. Its contraction and relaxation will help you to see nearby object and far off object. Understood?

[00:20:12]Shall we start our work please?

[00:20:15]>> Huh?

[00:20:18]See our near point is 25 cm. So if you will be going less than that you can't be able to see. Far off point is infinity. Nearby is how much? 25 cm. I hope you might have understood this one.

[00:20:34][clears throat] Now so these muscles settle the position of the islands. First thing we have already studied. They also control the focal length. Just now I talked they're controlling what? Focal length. Next these muscle together with suspensary ligament control the position of islands. So islands is intact in its position because of what we because of suspensary ligament and celiary muscles.

[00:21:08]I hope this much is easy. It is its function is to alter the focal length.

[00:21:13]That's what now camera focal length we can change. So here human eye focal length we can change by changing the lens size. I hope you might have understood. So that the image we can be able to focus on retina. So retina is that screen where the image is forming.

[00:21:31]Understood? So image formed there will get converted into electrical impulses and it is reaching to the brain.

[00:21:40]>> Yes. brain via optic nurse occupal loop it is going it is going occupal loop which loop >> occupal loop that time at the time of teaching control and coordination I will be explaining that sections also okay now we'll go back to the next part bita there is a thin delicate membrane made up of optical nerve fiber which cover most of the interior part of the eye that is known as retina what this is called as beta the screen is called But there is a thin delicate membrane.

[00:22:13]This is a thin and this membrane is delicate. Now you ask me now how a person is getting blind. There are two reasons for a person to become blind.

[00:22:23]One is called as retina detachment.

[00:22:29]One is called as retina detachment.

[00:22:31]Retina detachment is a case like many children now they're playing something something is happening suddenly some accident happened at that time actually what happened is the retina will get dislocated mean the frame the screen is in the place the lens got dislocated so because the lens dislocation will not allow the image to form on retina and because of that the person will not be able to have a vision understood so there are some type of problems which are temporary sometimes of problem which is permanent. Retina detachment will make you not blind but definitely if the angle is changed and the light is falling on blind spot means complete blind. Understood on so there are certain things that is exactly responsible for >> see one person Zerum has asked a very important question. See genetically also one reason is there how a child can be born blind since birth. But at the time of DNA formation now you please remember see at the time if a mother is taking some of the toxicated medicines of very high medicines that time see there are two reasons if parents are of close relations close relative marriages means the DNA is very very close because of that also many times the children are having eye defect this is one reason yes because the selection is not there selection is not there because of that the children are born with some deformities eye defect is a common one.

[00:24:06]Second is when there will be like the mother is taking having cancer or any type of disease which is very what you call taking a very high level of the toxicated medicines they're taking at that time the child body will get not only organs can get affected and I is a very delicate membrane also they can get affected.

[00:24:28]See thyroid is a disease that is passed on from mother to daughter. It's a gift a mother is giving to daughter. And thyroid is just a type of defect. It's a deficiency. Understood? Hypothyroidism and hypothyroidism is there.

[00:24:46]>> Huh?

[00:24:47]>> Yeah. In some cases, sons can also have thyroid.

[00:24:51]>> Mostly it is transferred to daughter mode. Understood? But sons means it will be and it will be easily detectable. I hope yes. Accident can also cause blindness.

[00:25:02]Accident is the major reasons of screwdriver. She but I feel like uh thyroid is genetical. Thyroid is genetical. Mother is the carrier and it will be transmitted to children. Okay.

[00:25:19]You keep on asking questions I'll answer. No problem for me.

[00:25:23]>> Yes.

[00:25:25]Yeah. I hope everybody understood this one now. So please remember there are certain type of eye defect the parents are giving to their children. You know eye cancer. Now there are certain type of eye cancer. It is genetically transmitted from parents to children.

[00:25:40]Eye defects are genetically transmitted if it is DNA coded means 100% coded means it will directly going from parents to children. Understood? You can't change that most of the eye defect. I hope everybody understood.

[00:25:55]Thyroid is a type of disorder beta it is iodine deficiency. iodine deficiency, hyperthyroidism and hypothyroidism. In this now it's a type of defect where the hormone your thyroxine hormone now maybe it will start secreted more then defect will the height will become very high some body deformities will be there that's why it is a case I will teach in control and coordination chapter hypo and hyperyroidism children I'll explain every part of it in more details right now we'll go to human eye and whatever questions you need to ask you can ask me I'm ready to answer your one gluccom is there now gluccom is also alo a type of eye defect understood or not it's also a type of eye defect genetical part genetics are see genetically DNA through DNA the eye defects can be transmitted okay you might have seen that the parents are using specs after sometime the childrens are also using specs that's a very common thing and most of the ID defects are generally genetically transmitted from parents to children but the biggest problem is close relative marriages if it is there means the chances of transmission is much higher.

[00:27:06]I hope children you have got your answer.

[00:27:11]See it is not see if your mother is having thyroid M the chances is 60 to 70% high but it will not be in this stage maybe in adolescence age when you will be reaching to another phase that time at the time of pregnancy or at the time when you will become little older the because it is now suppressive it can become dominative any time understood but yes they can be when the some body hormones level goes up and down now immediately it can be caught I I hope everybody understood this one about thyroid and everything. See I speak I'm not thinking like see if I will not speak mean who will speak. See if I will not speak about the things like what is correct. If I will not speak like when the thyroid so only for pregnant ladies now the doctors are gen they are going for thyroid test it's a compulsory test you know why because if thyroid is there mean the child born will be with some some type of defects. Understood? So that's why thyroid test is a very important test and you know what I speak at the time right now I'm I'm your mentor. I'm your teacher and I have to teach so that you are the future generation and you should be knowing all these things. Why to hide all these things understood? Not so in future generation in anyone in your family they're not going for thyroid test.

[00:28:27]Doctor is not taking thyroid test mean you can push your family member your sister your aunt that go for thyroid test which is very important for the coming child. I hope you might have understood this one. So now we'll talk about yellow spot. That's a very critical region. You know what there are two different type of cells present in the retina region. They are called as rods and cones. The rods and cones amount. In human eye the rods amount is less con amount is more. For animals now nocturnal animals. What is the meaning of nocturnal animals? Those animals which is exactly awaken in night they are called as nocturnal. They go for hunt in night. Correct. Now you will be seeing their eyes are glowing.

[00:29:10]Correct. Now so our eyes will not be glowing but some animals eyes are glowing. So you need to understand that their rods amount is more and cones amount is less so that they can have vision in night. And here for us rods amount is less and cones amount is more.

[00:29:28]So we can catch colors. Are you understanding? Because of cones amount is more. And rod's amount is less mean we can't see in dark night. I hope everybody understood this one. So this is exactly present where this is exactly present. No element owl is there. Aa bat can see.

[00:29:51]>> Bat can see.

[00:29:54]>> Bats are blind. They are sending sonic waves and the sonic wave ultra sonic waves. they sending sonic waves and the sonic waves they are catching back. So if any wall is there or anything will be there now they'll be able to the waves which is coming back. See if it is an empty space the waves will go and it will take time to come back. So they know that that is not a danger area. But if the waves they are sending it is coming back very fast. So what they doing? They're changing the angles.

[00:30:25]Understood or not?

[00:30:27]>> They are flying. That's what they that's a habit. You need to understand that that they are blind. I hope everybody understood this one. They send sound waves. Ah waves understood by sending from their mouth. Yes.

[00:30:41]>> Huh?

[00:30:42]>> Yeah. Yeah, the reflexes are we see you need to understand hey one blind person now they are much more knowledgeable than you because you know what you are seeing and you are perceiving they are not seeing keeping their another receptors active you need to understand children teach these things to everybody so yes they're changing their direction is absolutely correct yes another gener absolutely correct so you need to understand These things like the bats can change because of the waves they're sending and they are receiving. The next important information what we have learned say cones and rods. So human eye is having what self mode cones. So we can differentiate color got it rots less. So we can't see in night. [clears throat] Now we are going to talk about yellow spot a this is the critical part. So only I'm discussing about it. So now there is the thin delicate membrane.

[00:31:44]What is the name of that membrane?

[00:31:47]>> Retina. Understood? It is like a sheet.

[00:31:50]Optical nerve spread out throughout end in the form of rods and cones that two form the retina. At the center of the retina there is a yellow spot. So if retina is a sheet at the center of the sheet what is present yellow spot. What is the center present there is called as beta? yellow spot which is most sensitive to light. Please remember in retina the yellow spot is most sensitive to light and there is a patch of about how much is the width? 2 mm in diameter spread over the retina. So that's a circular patch. What is the mm? 2 mm.

[00:32:34]Diameter is 2 mm. So radius will be 1 mm. Okay. And the center of the yellow spot is slightly depressed. And this portion is about what is the depression portion? 0.25.

[00:32:48]And that is the diameter known as Kov centralis which contain only cones.

[00:32:55]Can I draw it? It will become easy for you.

[00:33:01]So once we are drawing it, it will become easy for you to understand. But can we talk about this retina? So this is retina. In retina there is a yellow spot.

[00:33:13]Got it. What is the diameter of the yellow spot? 2 mm. At the center of the yellow spot there is 4 V.

[00:33:23]Very small. And it is just like a slight depression. Depression means it is little bit backside like hump.

[00:33:31]Understood? Yes. So it's a slight depression present inside that is called as what bit.

[00:33:37]So yellow spot is what light sensitive talk first.

[00:33:44]See how much energy is taking four hours over here.

[00:33:50]Please understand this. This is what retina region. Inside retina region >> inside yellow spot.

[00:33:58]Understood. So when phobia phobia or phobia whatever you say what is there is they are little depressed and there the cones amount is more. So if the light is entering there you can be able to perceive the colors present in the universe. I hope you might have understood better. So what is this retina inside retina >> inside yellow spot?

[00:34:23]>> It is a depression or not?

[00:34:28]Yes, phobi means better a type a region.

[00:34:31]Fobi is just like you need to understand this a small region where con's amount is more and yellow spot is light sensitive and retina region is for vision.

[00:34:53]Why? because it is the one who is receiving light. Understood? The image is exactly formed on retina. So retina is the screen but all the places the image is not formed. Where it will be forming yellow spot in yellow spot where fing and there only you'll be able to see the color properly. I hope you might have understood this one. Children is it okay for all of you to understand this?

[00:35:18]Yes. That's what I am for this only now.

[00:35:21]If I will not clear the doubt means who will clear I will only read it out means is it understandable what is the diameter bit >> 0.25 mm very very less what is the diameter of yellow spot >> and what is the diameter of obi >> 0.25 very very less and beta it is having what cones only so it is exactly helpful for what light imparting and giving the color to it >> 0.25 25. Okay, next class we will do the next part because I think most of you are sleeping. By tomorrow morning 6:00, get ready and come. Bye everyone.