Question

A concave mirror of focal length f (in air) is immersed in water (μ= 4 / 3 ). The focal length of the mirror in water will be
(a) f
(b) $m= \frac{4}{3} f$
(c) $m= \frac{3}{4} f$
(d) $m= \frac{7}{3} f$

Answer 1

answer : option (a)

explanation : We know, law of reflection doesn't depend on refractive index of medium.

so, when A concave mirror of focal length f (in air ) is immersed in water then, the focal length of the mirror in water remains constant e.g., f.


[ note : law of refraction depends on refractive index of medium, that's why lens maker formula is given by, $\frac{1}{f}=(\mu-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$ where $\mu$ is refractive index of medium]

Answer 2

Answer:

options. a

Explanation:

Mirror focal length is constant.

R=2f , f = constant

Light Ray always travel in a straight line

reflection property and refraction property of mirror Radius and focal point is fixed