A point source of light S,placed at a distance L in front of the centre of a plane mirror of width d ,hangs vertically on a wall. A man walks in front of mirror along a line parallel to the mirror at a distance 2L as shown . the greatest distance over which he can see the image of light source in mirror is(1)d/2 (2) d (3) 2d (4). 3d

(4)

Since the mirror is a plane mirror so here u=v.. Hence if the man is in line with point light source and image then his distance from image is 3L. Draw a line joining image and man.. Length is 3L.. Man will get max range of view if he sees through edge of mirror.. so make a line passing through image point, mirror edge and then joining man.. you will get 2 triangles.. for small triancle mirror length=d/2 and length is L.. For larger triangle length of man to point is 3L and both these triangles are similar.. so the height is 3d/2.. This range is for upper half.. Same for lower half so total range is 3d..

Dear student,

Please find the answer to your question.

 

Since the mirror is a plane mirror so here u=v.. Hence if the man is in line with point light source and image then his distance from image is 3L. Draw a line joining image and man.. Length is 3L.. Man will get max range of view if he sees through edge of mirror.. so make a line passing through image point, mirror edge and then joining man.. you will get 2 triangles.. for small triancle mirror length=d/2 and length is L.. For larger triangle length of man to point is 3L and both these triangles are similar.. so the height is 3d/2.. This range is for upper half.. Same for lower half so total range is 3d..

 

Thanks and regards,

Kushagra