(a) A boy with a mouth 5 cm wide stands 2 m away from a plane mirror. Where is his image and how wide is the image of his mouth?(b) The boy walks towards the mirror at a speed of 1 m/s. At what speed does his image approach him?

(a) The image will form 2m behind the mirror and 5 cm wide. The reason being, the characteristic of plane mirror, which states that a plane mirror forms an image of the same size as the object, and at the same distance behind the mirror as that of the object from the mirror.

(b) When the boy walks towards the mirror at a speed of 1 m/s, his image will also appear to move towards the mirror at the same speed of 1 m/s. So, the speed at which his image approaches him will be 2 m/s + 2 m/s = 4 m/s.

Explanation with the image is posted for reference only.

Characteristics of the image formed by a plane mirror are virtual, erect (upright), of the same size, laterally inverted and at the same distance.

Plane mirrors are used in kaleidoscopes, shaving mirrors, dentists' mirror, torch lights, etc.