Question

when an object is placed 20cm from a concave mirror a real image magnified three times is for better if find the image distance and focal length ​

Answer 1

Explanation:

In concave mirror

object distance(u) = -20cm

Magnification(m) = -v/u=3

= -v/-20=3

= v=60cm

Image distance(v) =60cm

According to the formula of mirror

1/v+1/u=1/f

=1/60+1/-20=1/f

=1/60-1/20=1/f

=1-3/60=1/f

= -2/60=1/f

= f= -30cm

Ans-image distance =60cm

Focal length = 30cm