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Given figures show the arrangements of t...

Given figures show the arrangements of two lenses. The radii of curvature of all the curved surfaces are same. The ratio of the equivalent focal length of combinations P, Q and R is ......

A

`2:2:1`

B

`1:1:1`

C

`1:2:2`

D

`2:1:1`

Text Solution

Verified by Experts

The correct Answer is:
A, B

In given diagram P, Q and R lenses are in contact.
`therefore` For P combination of lenses,
`(1)/(F_P)=1/f+1/f=2/f`
`[because 1/F=(1)/(f_1)+(1)/(f_2)` for combination of lenses]
or `F_P=f/2`
Similarly for Q and R combination.
`F_Q=f/2" and "F_R=f/2`
Therefore, `F_P`: `F_Q`: `F_R` is equal to 1:1:1
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