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In figure, an air lens of radius of curv...

In figure, an air lens of radius of curvature of each surface equal to `10 cm` is cut into a cylinder of glass of refractive index `1.5.` The focal length and the nature of lens are

A

15 cm, concave

B

15 cm, convex

C

`infty`, neither concave nor convex

D

0, concave

Text Solution

Verified by Experts

The correct Answer is:
A
`(1)/(f) = (n_(ag) -1) ((1)/(R_(1)) - (1)/(R_(2)) )`
`rArr " " (1)/(f) = ((2)/(3) -1) ((1)/(10) + (1)/(10) )`
`rArr (1)/(f) = (-1)/(3) xx (2)/(10) rArr f = 15 ` cm .
Hence, behave as concave lens.
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