A) Increases by 4%
B) Increases by 2%
C) Decreases by 2%
D) Decreases by 4%
Correct Answer: D
Solution :
Intensity\[\propto \frac{1}{{{r}^{2}}}\] \[\Rightarrow \] \[\frac{{{I}_{2}}}{{{I}_{1}}}={{\left( \frac{{{r}_{1}}}{{{r}_{2}}} \right)}^{2}}={{\left( \frac{{{r}_{1}}}{{{r}_{1}}(1+2%)} \right)}^{2}}\] \[\Rightarrow \] \[{{I}_{2}}={{I}_{1}}{{(1+2%)}^{-2}}\] Expanding by binomial theorem \[\Rightarrow \] \[{{I}_{2}}={{I}_{1}}(1-4%)\] \[\therefore \]Intensity decreases by\[4%\].
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