Optics 7 Question 31
32. The intensity of light at a distance $r$ from the axis of a long cylindrical source is inversely proportional to $r$.
$(1981,2 M)$
Integer Answer Type Questions
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Solution:
- At a distance $r$ from a line source of power $P$ and length $l$, the intensity will be,
or
$$ \begin{gathered} I=\frac{P}{S}=\frac{P}{2 \pi r l} \\ I \propto \frac{1}{r} \end{gathered} $$
