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 s
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
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Correct Answer - B
Magnification,
`m=(f)/(f-u)rArr -3=(f)/(f-(20))`
`rArr " "` The focal length of mirror, `f =-15 cm`
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