Vimal Raj asks:
“A thick plane mirror forms a number of images of a point source of light . which image is brightest ?”
Answer: In the case of a thick plane mirror, reflection takes place at the two surfaces, (top and bottom surfaces) and images are formed due to both. The second surface is silvered and therefore the second image is the brightest. Further images are formed due to multiple reflections and due to absorption of light by medium the images become fainter.
If the front surface of the mirror is silvered, only one image will be formed.