Question

(i) Find the size, nature and position of image formed when an object of
size 1cm is placed at a distance of 15cm from a concave mirror of focal
length 10cm.


(ii) The absolute refractive index of Ruby is 1.7. Find the speed of light in
Ruby. The speed of light in vacuum is 3×108 m/s.​

Answer 1

Explanation:

u=−15cm

f=−10cm

h=1cm

From mirror formula

f

1

=

u

1

+

v

1

v

1

=

f

1

−

u

1

v

1

=

−10

1

−

−15

1

v=−30cm

The image is formed at a distance 30cm on the left side of the mirror from the pole.

m=

h

h

′

=

u

−v

h

′

=−1×

−15

−30

h=−2cm

The image size is 2cm and it is real and inverted