Question
Question: A concave mirror of focal length $f$ (in air) is immersed in water ($\mu=4/3$). The focal length of ...
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
\frac{4}{3}f
C
\frac{3}{4}f
D
\frac{7}{3}f
Answer
f
Explanation
Solution
The focal length of a spherical mirror is determined by its radius of curvature, R, where f=2R. The radius of curvature is a physical property of the mirror's shape and does not change with the surrounding medium. Reflection follows the law of reflection, which is independent of the medium. Therefore, the focal length of a mirror remains unchanged regardless of the medium it is placed in. The refractive index of water is irrelevant to the focal length of the mirror.