Answer:
a) 0.08 W/m² b) 0.64*10⁶ W/m²
Explanation:
a) Assuming that the lightbulb behaves as a point source, it radiates energy evenly in all directions, so the power spreads out over the surface of a sphere of radius equal to the distance to the object being illuminated.
The expression for intensity, in this particular case, is as follows:
[tex]I =\frac{P}{A} (W/m2) = \frac{4.0 W}{4*\pi*(2.0m)^{2} } = 0.08 W/m2[/tex]
b) In the case of light produced by a laser source, the beam is not spread out throughout space, so we can simply define the intensity as power divided by the area of the beam, assumed circular, as follows:
[tex]I =\frac{P}{A} (W/m2) = \frac{2.0 W}{\pi*(0.001m)^{2} } = 0.64e6 W/m2[/tex]
⇒ I = 0.64*10⁶ W/m²
