A number of images of a candle flame can be seen in a thick mirror. The brightest image is

The correct option is B Second

A thick plane mirror forms number of images due to multiple reflections.

The first image is due to a weak reflection (most of the light is refracted) from front glass surface, therefore we get a fainter first image.

The second image is due to a strong reflection from back-silvered surface surface, which is a very good reflector of light, therefore we get a brightest second image.