Question

a convex lens placed between an object and a screen 180 centimetre apart forms a real image on the screen if the distance of the object from the lens is 30 cm calculate the focal length and power of the lens​

Answer 1

Answer:

f=

4D

D

2

−Δ

2

this is formula of finding focal length using displacement method.

f:− focal length

Δ:− displacement of lens done in order to get image again on screen.

D:− distance between object and screen.

f=

4×10

10

2

−2

2

f=2.4 cm