Question

A 2.0 cm high object is placed at a distance of 20 cm from a concave mirror. A
real image is formed at 40 cm from the mirror. Calculate the focal length of the
mirror and the size of the image.

Answer 1

Answer:

Since the image is real.

So the distance of image from mirror is v=−40 cm

The distance of image from object is u=−20 cm

We know ,

f

1

=

v

1

+

u

1

=

−40

1

+

−20

1

f=

3

−40

cm

Now the magnification m=−

u

v

=−2

Height of object h=2cm

Height of image h

1

=∣m∣×h=2×2=4cm