Question

describe that a normally incident ray is un-deviated

Answer 1

Answer:

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Explanation:

Any light ray incident on the optical center can be viewed as incident on the center of a circle of which the less is a part.Hence, we can say that this light ray is incident normally on the lens. Now, we know that any normal incidence goes undeviated through the medium. Hence, a light ray incident on optical centre passes undeviated through it after refraction.

Answer 2

Explanation:

we can prove that a ray, falling at an angle of 90° on the interface, between a pair of rarer and denser medium passes undeviated... by Snell's Law.

i.e angle i = angle r = 90°

let the speed of light changes from v1 to v2 .

then ,

sin i / sin r = v1/ v2

or,. v2× sin i = v1× sin r

or,.

v2× sin 90°= v1 × sin r

or,.

v2× 0. = v1× sin r

0. = v1× sin r

But v1 can't be 0 ,

Hence,

sin r = 0

sin r = sin 90°

or,

r= 90°

Here we see that,

angle i = angle r = 90°

Hence, no bending occurred.