A concave lens and a convex mirror both are dipped in an oil of refractive index 1.2. The focal length of:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → lens will change but of mirror will remain same
The focal length of a mirror is determined solely by its radius of curvature (R) -
$R=\frac{f}{2}$
Since mirrors rely refraction unlike lens, the refractive index of a medium has no effect on the focal lenght.