Question

1)A plane mirror moved toward a body at rest position by one cm , What is the distance between the first image and the second image ? proof


2)A body stands in front of image then the body itself moved one meter toward the plane mirror, What is the distance between the first image and the second image ? proof

There is a difference between the two distances , isn't there ?

Answer 1

no 1 answer=> Detailed explanation is here: Distance of Image formed in the mirror is same as the distance of the object form the surface of the mirror.

Thus is distance of object = u

Then distance of image = -u (as the image is formed at other side of the mirror)

Thus distance between image and object = 2u ...(1)

Now if mirroe is approaching you/object with speed v, then distance travelled by mirror in unit time = v units

Thus distance between mirror and object in unit time = u - v

Thus disatnce between object and its image = 2(u-v)....(2)

From equations (1) and (2) distance between image and object is reduced by 2v units in unit time(1 second)

Thus speed of image w.r.t object = 2v

no 2 answer=> The image formed in a plane mirror is as far behind the mirror as the object is in front of it, i.e. the distance between the object and the mirror (u) is the same as the distance between the mirror and the image (v). Distance between object (boy) and the image is u + v = 2m + 2m = 4m.