Question

when an object is placed at the distance of 15cm from a convex lens and the enlargement is 3, what is the power of that lens?​

Answer 1

Explanation:

u = 15 cm

magnification = 3

m= -v/u

3= -v/15

- v = 45 cm

so then find out the value of focal length and find it's reciprocal

Answer 2

Explanation:

For the lens,

v

1

−

u

1

=

f

1

v

1

=

10

1

−

15

1

Thus, v=30cm

Now, for the mirror, this image acts as the object.

u=30−10=20cm

Also, v=−25cm

Hence,

25

−1

+

20

1

=

f

1

f=100cm