Question

(15. An object of height 1.5 cm is situated at a distance
of 15 cm from a concave mirror. The concave
mirror forms its real image of height 3.0 cm. The
focal length of concave mirror will be
(1) – 10 cm (2) - 20 cm (3) 20 cm (4) 30 cm​

Answer 1

Answer:

ANSWER

Given,

object height h

1

=1.5 cm

real image length h

2

=−3cm

Position of object from the mirror u=−15cm

Mirror magnification formula

m=

h

1

h

2

=−

u

v

1.5

−3

=

−15

−v

v=−30cm

Apply Mirror formula

f

1

=

−30

1

+

−15

1

f=−10cm

December 26, 2019