JEE Main 2025 (Online) 24th January Morning Shift | Geometrical Optics Question 30 | Physics

A thin plano convex lens made of glass of refractive index 1.5 is immersed in a liquid of refractive index 1.2. When the plane side of the lens is silver coated for complete reflection, the lens immersed in the liquid behaves like a concave mirror of focal length 0.2 m . The radius of curvature of the curved surface of the lens is

0.15 m

0.10 m

0.25 m

0.20 m

JEE Main 2025 (Online) 24th January Morning Shift

MCQ (Single Correct Answer)

-1

A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of $f_1$ in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of $f_2$ when it is immersed in a liquid of refractive index 1.2. If both the lenses are made of same glass of refractive index 1.5 , the ratio of $f_1$ and $f_2$ will be

$2: 3$

$1: 3$

$1: 2$

$3: 5$

JEE Main 2025 (Online) 23rd January Evening Shift

MCQ (Single Correct Answer)

-1

A concave mirror of focal length $f$ in air is dipped in a liquid of refractive index $\mu$. Its focal length in the liquid will be:

$\mu f$

$f$

$\frac{f}{\mu}$

$\frac{f}{(\mu-1)}$