Question

find the position of object which when placed infront of a concave mirror of focal length 20cm produces a virtual image which is thrice the size of the object. ​

Answer 1

Answer:

Given f=-20cm m=+2 because the image is virtual and erect.

−

u

v

=2 v=−2u

f

1

=

u

1

+

v

1

−20

1

=

u

1

−

2u

1

−20

1

=

2u

1

2u=−20

u=−10cm

so the object is placed at a distance of 10cm from the mirror.