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A plano-convex lens of focal length 30 c...

A plano-convex lens of focal length 30 cm has its plane surface silvered. An object is placed 40 cm from the lens on the convex side. The distance of the image from the lens is

A

18 cm

B

24 cm

C

30 cm

D

40 cm

Text Solution

Verified by Experts

The correct Answer is:
B


`(1)/(F)=(1)/(f_l)+(1)/(f_m)+(1)/(f_l)`
`=(2)/(f_l)+(1)/(infty)=(2)/(30)impliesF=15cm`
The silvered lens behaves as concave mirror of focal length `15 cm`
`(1)/(v)+(1)/(u)=(1)/(f)implies(1)/(v)+(1)/(-40)=(1)/(-15)`
`(1)/(v)=-(1)/(15)+(1)/(40)=(-8+3)/(120)impliesv=-24cm`
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Knowledge Check

  • A convex lens of focal length 15 cm is placed on a plane mirror. An object is placed at 30 cm from the lens. The image is

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