JEE Main 2025 · 2 April · morning · Single correct · +4 / −1
A spherical surface separates two media of refractive indices 1 and 1.5 as shown in figure. Distance of the image of an object ' O ', is :
( C is the center of curvature of the spherical surface and R is the radius of curvature)
- (a) 0.24 m left to the spherical surface
- (b) 0.24 m right to the spherical surface
- (c) 0.4 m left to the spherical surface
- (d) 0.4 m right to the spherical surface
Answer and solution
Answer (c) 0.4 m left to the spherical surface
Solution
Physics sir · 3 steps
Put the signs in first, from the surface along the light, and the formula does the rest.
- Set the signs. Light travels left to right, and distances are measured from the surface. The object is on the left, so u = -0.2 m. C is on the right, so R = +0.4 m. Here n₁ = 1 and n₂ = 1.5.
n₂/v - n₁/u = (n₂ - n₁)/R
- Put in numbers. 1.5/v - 1/-0.2 = 0.5/0.4, so 1.5/v + 5 = 1.25. That gives 1.5/v = -3.75, so v = -0.4 m.
- So. The negative v means the image is on the same side as the object. It is a virtual image 0.4 m to the left of the surface, which is option (c).
The idea to keep. For refraction at a curved surface, fix the signs of u and R from the figure before using n₂/v - n₁/u = (n₂ - n₁)/R. The sign of v then tells you which side the image is on.
Answer from the NTA final answer key. Solution by PrepWiser.