A) 100 : 1
B) 104 : 1
C) 1 : 100
D) 1 : 104
Correct Answer: B
Solution :
\[I\propto \frac{1}{{{r}^{2}}}\] so, \[\frac{\text{Illuminance on slide }}{\text{Illuminance on screen}}=\frac{{{(\text{Length of image on screen)}}^{\text{2}}}}{{{(\text{Length of object on slide)}}^{\text{2}}}}\] \[={{\left( \frac{3.5\ m}{35\ mm} \right)}^{2}}={{10}^{4}}:1\]
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