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An image of a candle on a screen is foun...

An image of a candle on a screen is found to be double its size. When the candle is shifted by a distance of 5cm, then the image becomes triple its size. Find the nature and radius of curvature of the mirror.

A

concave, 60 cm

B

convex, 60 cm

C

concave, 30 cm

D

convex 30 cm

Text Solution

Verified by Experts

The correct Answer is:
A
Sinnce the image is formed on screen it is real. Real object and real image implies concave mirror
applying `m=f/(f-u)` or `2=f/(f-(-u))`…(1)
after shifting `-3=f/(f-(u+5))` …(2)
[ why M + 5 ?, why not M - 5: In a concave mirror, are size of real image will increase, only when the real object is brought closer to the mirror. In doing so, its x coordinate will increase ] from(1)& (2) we get f = -3Qcm or R = 60cm
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