An object is 20 cm away from a concave mirror with focal length 15 cm. If the object moves with a speed of 5 m/s along the axis, then the speed of the
An object is 20 cm away from a concave mirror with focal length 15 cm. If the object moves with a speed of 5 m/s along the axis, then the speed of the image will be
A. 45 m/s
B. 27 m/s
C. 9 m/s
D. 10 m/s
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Correct Answer - A
(a) We have, `1/v-1/u=1/f`
`rArr1/v-1/20=1/(-15)`
v=-60 m
Image speed=`(v^(2)/u^(2))` (object speed)
`=(60/20)^(2)(5)`=45 m/s
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