SSC MTS EXAM

SSC

PHYSICS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
The radius of curvature of a mirror is 20cm the focal length is
A
20 cm
B
10 cm
C
40 cm
D
5 cm
Explanation: 

Detailed explanation-1: -So, focal length = 21× radius of curvature = 21×20 cm = 10 cm.

Detailed explanation-2: -For concave mirror f=2R=2−20=−10 cm.

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