Question

At what distance in front of a concave mirror of focal length 10 cm, an object be placed so that its real image of size five times that of the object is obtained?

Answer 1

The object should be placed at a distance of 40cm

Focal length = f = 10cm

Linear magnification = m = I/O

where I is size of the image and O is size of the object

Since, real time is five times of the object, thus I = 50

m = 50/0 = m = -5

Linear magnification = m = f-u/f

5 = 10-u/10

50 = 10-u

u = 40

Therefore, the object should be placed at 40 cm in front of the convex mirror. where −ve sign represents that the object is placed on the left side of the mirror.

Answer 2

Answer:

The object should be placed 12cm in front of the mirror