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A concave mirror gives an image three ti...

A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be

A

10 cm

B

15 cm

C

20 cm

D

30 cm

Text Solution

Verified by Experts

The correct Answer is:
B
(b) Magnification,
`m=(f)/(f-u) rArr -3=(f)/(f-(-20))`
`rArr` The focal length of mirror, f=-15 cm
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