Question

A concave lens made of a material or refractive index n1 is kept in a medium of refractive index n2 A parallel beam of light is incident on lens. Trace tha path of light parallel to principal axis incident on concave lens after refraction when:

n1>n2
n1=n2
Give reasons for each

Answer 1

(a) In this case, n1 > n2, i.e. medium of concave lens is denser than the medium from where light ray
is incident on it. Therefore, at entering surface, the light ray bends towards the normal N1, while leaving the lens, the ray again goes under refraction at leaving surface and in this situation it bends away from the normal N2.

(b) In this situation, light ray parallel to principal axis goes straight without any deviation as
n1 =n2

Answer 2

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