Question

convex lens when placed in a certain medium does not at all act as a lens. The refractive index of lens in n, and that of medium is ny. What is the relation between n, and n,?
a) n1 > n2
b) n1 < n2
c) n1 = n2
d) none of these​

Answer 1

Answer:

When n1 <n2, light goes from rarer to denser medium. Therefore, on passing through a convex lens, it converges.

(i) When n1 = n2, there is no change in medium. Therefore, no bending or refraction occurs as shown in figure.

(ii) When n1 >n2 , light goes from denser to rarer medium. Therefore, no passing through a convex lens, it diverges as shown in figure.

Answer 2

Given:

A convex lens when placed in a certain medium does not at all act as a lens. The refractive index of lens in n1, and that of medium is n2.

To find:

Relation between n1 and n2?

Solution:

• Since the question says that " CONVEX LENS DOES NOT ACT AS A LENS", it means that light rays passing through the convex lens does not undergo any refraction or deviation.

This is possible only when :

• The refractive index of the convex lens and that of the medium is equal. Hence, while passing through the lens the light ray does not experience any change in velocity and hence does not undergo any deviation.

So, n1 = n2.

$\star$ Hope It Helps.