Question

52. When an object is placed at a distance of 40 cm from a concave mirror the size of
the image is one-fourth that of the object.
(i) Calculate the distance of the image from the mirror.
(ii) What will be the focal length of the mirror?​

Answer 1

Explanation:

Initially:

u

i

=−40cm f

i

=−15cm

v

i

1

+

u

i

1

=

f

1

v

i

1

+

−40

1

=

−15

1

⇒v

i

=−24cm

Finally: u

f

=−20cm f=−15cm

v

f

1

+

u

f

1

=

f

1

∴

v

f

1

+

−20

1

=

−15

1

⇒v

f

=−60cm

Thus image is shifted by 60−24=36cm

.... pls mark as brainliest

Answer 2

Answer:

Given =  40m

Magnification m = v/u = 1/4

v = 40 x 1/4 = 10 cm

Using mirror formula

1/v + 1/u = 1/f

Using with proper sign

1/f = -1/40 - 1/10

1/f = -50/400 = -1/8

So f = -8m

So focal of the concave mirror = 8m