Question

An object is placed at 20cm in front of a concave mirror of curvature 20 cm state the nature and size of the image relative to that of the object? answer​

Answer 1

Answer:

Given : Object distance, u=−20 cm

A concave mirror forms a real magnified image only when the image to be formed is inverted i.e. m=−3

Magnification m=

u

−v

∴ −3=

−20

−v

⟹v=−60 cm

Using mirror formula :

v

1

+

u

1

=

f

1

∴

−60

1

+

−20

1

=

f

1

⟹ f=

4

−60

=−15 cm

Thus focal length of the mirror is 15 cm.