Question

Power of point source is 18mW. Intensity from 2.5m away ?

Answer 1

Given that,

Power of a point source is 18 mW or 0.018 W

To find,

The intensity from 2.5 m away

Solution,

Intensity at certain distance is is given by :

$I=\dfrac{P}{4\pi r^2}$

Plugging all the values in above formula such that,

$I=\dfrac{18\times 10^{-3}}{4\pi \times (2.5)^2}\\\\I=2.29\times 10^{-4}\ W/m^2$

So, the intensity of source is $2.29\times 10^{-4}\ W/m^2$.

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Intensity

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