**Problem : **
Compute the energy density of a 2.0 mW laser beam with a diameter of 2mm.

**Problem : **
The power per unit area incident on the earth due to sunlight is about
1.4
kW/m
^{2}
. What is the
approximate magnitude of the electric field vector on sunlight near the earth (
*μ*
_{0}âÉá4*Π*×10^{-7}
N.s
^{2}
/C
^{2}
)?

**Problem : **
Write an expression (in SI units) for the magnetic field of a 10 MHz light wave traveling in the negative
*z*
direction and an electric field amplitude of
.

**Problem : **
Consider the following electric and magnetic waves:

= | |||

= |

Show that these waves satisfy Maxwell's equations in free space. What conditions must be satisfied? First we have â??. which is clearly satisfied since the magnetic field is traveling in the

**Problem : **
Consider a 60W light bulb. Assume that all radiation given off is in the form of light of
wavelength 650 nm. Calculate the number of photons given off per second.

Take a Study Break!