Question

when an object is placed at a distance of 15 cm throw a concave mirror its image is formed at 10 cm in front of the mirror calculate the focal length of the mirror ​

Answer 1

$u = - 15 \\ v = 10 \\ f =$
1/f = 1/u - 1/v
1/f= 1/-15 - 1/10
1/f=2 -3/30
1/f=1/30
Therefore f = 30cm..
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