Question

A plane mirror forms image $I$ of an object O kept 10 cm from the mirror. It is found that when a Plano concave thin lens is placed in front of and in contact with the mirror (plane surface of lens in contact with mirror), the position of image formed by plane mirror does not change. Then the refractive index of lens and radius of curvature of its curved surface are respectively:

• A. 1.5, 10 cm
• B. 2.5, 10 cm
• C. $\sqrt{2},10cm$
• D. All of these are possible

Answer 1

The correct option is D All of these are possible

We know from the laws of refraction, that the image will be formed at the same distance as the object from the optical centre only when the object is placed at the centre of curvature.
That is, all that matters is that the objects should be placed at the centre of curvature of the concave lens not the refractive index of the lens