Question

The magnification of a real image produced by a concave mirror of radius of curvature 20cm is 3. The IMAGR DISTANCE is ?

Answer 1

In case of spherical mirror

Magnification, m= v/u and

1/f=1/v + 1/u ( mirror formula)

Multiplying the above equation by v both sides, we get

v/f= v/v + v/u

Further simplifying, we get

v/f= 1 + m         equation 1

Given that

m= 3 and

R= 20 cm

we know that R=2f, so

f= R/2= 20/2= 10 cm

using sign convention for concave mirror

f= -10 cm

plugging these value in equation 1, we get

v/(-10)= 1+ 3

v= 4*(-10)

v= -40

Therefore, the distance of image is formed 40 cm away from the pole of the mirror and left to the mirror.