If separation between screen and point source is increased by 2%, what would be the effect on the intensity?

Increases by 4%

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Increases by 2%

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Decreases 2%

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Decreases by 4%

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Solution

The correct option is D Decreases by 4%
$I = \frac{1}{r^{2}}$ or $I \propto r^{- 2}$
% Change in $I = (- 2) \times$ % change in $r$
$= (- 2) (+ 2) = - 4$ %.

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If separation between screen and point source is increased by 2%, what would be the effect on the intensity?

The correct option is D Decreases by 4%I=1r2 or I∝r−2% Change in I=(−2)× % change in r =(−2)(+2)=−4%.

The correct option is D Decreases by 4%
$I = \frac{1}{r^{2}}$ or $I \propto r^{- 2}$
% Change in $I = (- 2) \times$ % change in $r$
$= (- 2) (+ 2) = - 4$ %.