Hello friends
Well come to the follow up of previous post about defective vision. In previous post, I tried to keep writing humourous and casual but it seems, except a few, everyone here is very serious. So I'll be direct to what caption says.
👉 I assume , we have well known about optics and it's behaviour. I will still be very short to introduce them but not in a copy paste way.
Refraction :
When rays of light pass through a transperrent medium, we call it refraction. Observation says, when a ray of light crosses a medium, it always gets deflected into the second medium.This unique behaviour of light does help to correct our defective vision. We will get there soon but before that, Here is a super quick graphical example of refraction and deflection of light:
[ Prepared by me]
In the above picture, light passes from lighter medium to denser medium and in this case after refration, the ray reflects towards normal (the assumed perpendicular in black colour).
👉 If the ray goes from denser medium to light medium, it will deflect outward from the normal. Real observation does prove it. [Try it drawing yourselves]
Lens:
Any transparent medium can be called a lens. In case of lens, Air becomes lighter medium and the lens itself becomes denser. When a ray of light penetrates from air to lens , it too gets diverted and when again it comes out of the lens from its opposite side, it deflects again. Let's head to a quick example:
[Prepared by me]
We have seen when rays of ligh pass through a Convex Lens, they get closer to each ohter as they advance. We call it converging lens.
👉 In case of Concave Lens, they will spread and keep increasing distance between them as they advance.We call it diverging lens. [ Try it drawing yourselves]
Eye defection:
👁️🗨️ Technical term Myopia, we call it shortsightedness. Our vision limits to close range. Correction: Expectacles of concave/diversing lens.
👁️🗨️ Technical term Hypermetropia, we call it longsightedness. We cant see objects in closer. Our eye lens can't focus in close range. Correction: Expectacles of convex/convering lens.
👁️🗨️ For older people whose eyes can neither focus in close range nor in the distance, there is a bi-focul lens. It helps them see both objects in the distance and near.
👁️🗨️ Astigmatism is another defection. In this case, it seems an object gets cut off from the edge. We have cylindrical lens to correct it.
👉 I have shortsightedness, the first one mentioned above. Now I am gonna make diagram with an human eye, a concave lens and an object in the distance. We will check how does it helps our eyes to make focus in the distance.
But before that I want to discuss, in short ofcourse, how and why my eyes aren't able to focus in the distance. May be my eye balls get elongated from behind and so focus has come in closer distance. How? May be deficiency of vitamin from morning. So, Doctors said they couldn't make eye balls a perfect shape but what they could do is giving my eyes lens to stop further elongation from behind.
👉As concave lens tries to diverge rays of light , the focous goes to object in the distance. Adjusting angle of curvature of lens, focus can be put on object. When doctors in clinic test your eye power, they use lens of different curvature to get a perfect match for you.
Try drawing a correction of hypermetropia usinig a convex lens on your own.
That's all for today. I hope you have got a idea how it works. Excuse me if drawing seems improper.By the way, All of them are hand made.
Thank you so much for stoping by.
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