The separation between the screen and a concave mirror is 2r. An isotr – McqOptions

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1.	The separation between the screen and a concave mirror is 2r. An isotropic point source of light is placed exactly midway between the mirror and the point source. Mirror has a radius of curvature r and reflects 100% of the incident light. Then the ratio of illuminances on the screen with and without the mirror is
A.	10 : 1
B.	2 : 1
C.	10 : 9
D.	9 : 1
Answer» C. 10 : 9

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