Question

Light from a laser forms a 1.31-mm diameter spot on a wall. If the light intensity in the spot is what is the power output of the laser?

Answer 1

Answer:

0.04973 W

Explanation:

I = Intensity of laser = $3.69\times 10^4\ W/m^2$ (assumed, as it is not given)

d = Diameter of spot = 1.31 mm

r = Radius = $\dfrac{d}{2}=\dfrac{1.31}{2}\ mm$

A = Area = $\pi r^2$

Power is given by

$P=IA\\\Rightarrow P=3.69\times 10^4\times \pi \dfrac{(1.31\times 10^{-3})^2}{4}\\\Rightarrow P=0.04973\ W$

The power output of the laser is 0.04973 W