The refractive index of the material of a concave lens is `n`. It is immersed in a medium of refractive index `n_(1)`. A paprallel beam of light is incident on the lens. Trace the path of emerged rays in each of the following cases :
(a) `n_(1) gt n` (b) `n_(1) lt n` ( c) `n_(1) = n`.

Explanation

The path of the emergent rays in the three cases are shown in Fig.
(a) As `n_(1) gt n`, light goes from denser to rarer medium. Therefore, in passing through a concave lens, it converges instead of diverging as shown in Fig.
(b) As `n_(1) lt n`, light goes from rarer to denser medium. Therefore, in passing through a concave lens, it diverges as shwon in Fig.

(c ) As `n_(1) = n`, there is no change in medium on passing through a concave lens. Hence there is no bending/refraction. The rays continue along tneir original path, as shown in Fig.