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A double convex thin lens made of glass ...

A double convex thin lens made of glass (refractive index `mu = 1.5`) has both radii of curvature of magnitude 20 cm . Incident light rays parallel to the axis of the lens will converge at a distance L such that

A

L = 20 cm

B

L = 10 cm

C

L = 40 cm

D

L = 20 / 3 cm

Text Solution

Verified by Experts

The correct Answer is:
A
`(1)/(f) = (n- 1) ((1)/(R_(1)) - (1)/(R_(2)))`
`rArr (1)/(f) = (1.5 - 1) ((1)/(20) + (1)/(20) ) rArr = 20 cm `
Parallel rays converge at focus.
So, L = f .
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