We can reasonably model a 90-w incandescent lightbulb as a sphere 7.0cm in diameter. typically, only about 5% of the energy goes to visible light; the rest goes largely to nonvisible infrared radiation.
a) what is the visible light intensity at the surface of the bulb?
b) what is the amplitude of the electric field at this surface, for a sinusoidal wave with this intensity?
c) what is the amplitude of the magnetic field at this surface, for a sinusoidal wave with this intensity?

292.3254055 W/m²

469.26267 V/m

Explanation:

P = Power of bulb = 90 W

d = Diameter of bulb = 7 cm

r = Radius =

= Permittivity of free space =

c = Speed of light =

The intensity is given by

5% of this energy goes to the visible light so the intensity is

The visible light intensity at the surface of the bulb is 292.3254055 W/m²

Energy density of the wave is

Energy density is also given by

The amplitude of the electric field at this surface is 469.26267 V/m

Amplitude of a magnetic field is given by

The amplitude of the magnetic field at this surface is

answer: electrons