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An object is placed 5 cm from the pole of a concave mirro...

An object is placed 5 cm from the pole of a concave mirror. if the focal length of the mirror is 10 cm. what is the image distance?

A.

10 cm in front of the mirror

B.

5 cm in front of the mirror

C.

10 cm behind the mirror

D.

5 cm behind the mirror

Correct answer is C

u = 5 cm , f = 10 cm, v = ?
(1)/v + (1)/u = (1)/f
(1)/v + (1)/5 = (1)/10
= (1)/v = (1)/10 - (1)/5

= (1 - 2)/10 = (1)/10
∴ v = - 10 cm
∴ The image is 10 cm behind the mirror