A) 10 : 1
B) 2 : 1
C) 10 : 9
D) 9 : 1
Correct Answer: C
Solution :
The illuminance on the screen without mirror is \[{{I}_{1}}=\frac{L}{{{r}^{2}}}\] The illuminance on the screen with mirror is \[{{I}_{2}}=\frac{L}{{{r}^{2}}}+\frac{L}{{{(3r)}^{2}}}=\frac{10}{9}\times \frac{L}{{{r}^{2}}}\] \[\therefore \frac{{{I}_{2}}}{{{I}_{1}}}=\frac{10}{9}=10:9\]You need to login to perform this action.
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