Two plano convex lenses of same material and of focal lengths 20 cm & 5 cm should be arranged such that the combination is free from chromatic aberration. Then effective focal length of the combination will be:

20 cm

4 cm

12.5 cm

8 cm

A

20 cm

B

12.5 cm

C

8 cm

D

4 cm

Open in App

Solution

Verified by Toppr

The effective focal length of the lens is,

1f=1f1+1f2−f1+f22f1f2

Substituting the respective values, the effective focal length obtained is, f=12.5

Was this answer helpful?

0

Similar Questions

Q1

Two plano convex lenses of same material and of focal lengths 20 cm & 5 cm should be arranged such that the combination is free from chromatic aberration. Then effective focal length of the combination will be:

View Solution

Q2

Arrange the following combinations in the increasing order of focal length : a) Two plano convex lenses of focal lengths 20 cm and 30 cm in contact. b) Two convex lens of focal lengths 20 cm and 10 cm in contact. c) Two convex lenses of focal length 25 cm separated by 5 cm.

View Solution

Q3

Two plano-convex lenses of same material and of focal lengths f and 2f are coaxially separated by a suitable distace to minimize chromatic aberration. The equivalent focal length of the combination is

View Solution

Q4

A convex lens of focal length 10 cm is placed in contact with a concave lens of focal length 20 cm. The focal length of this combination of lenses will be:
(a) +10 cm
(b) +20 cm
(c) −10 cm
(d) −20 cm

View Solution

Q5

Two plano convex lenses of focal lengthsf1 andf2 set for minimising spherical aberration are kept apart by 2 cm. If the equivalent focal length of combination is 10 cm, the values of f1 and f2 are :