Question

When a spherical mirror is faced towards sun a real and highly diminished image of sun formed at 15cm from it by using this mirror where should an object be placed to get 3 times magnified image

Answer 1

The object must be kept at 10 cm to get 3 times magnified image.

Since object is at infinity and a real and diminished image is formed, it is therefore a concave mirror.

Mirror formula

where v is distance of image from the mirror

and u is distance of object from mirror

f is focal length which in this case is -15cm as object placed in infinity makes image at focus point.

Magnification formula m= -

v = -3u

- = - +

- =

u = -10cm

So object should be placed at 10 cm before the mirror to get 3 times magnified image.