Answer
(a) $I = 40~W/m^2$
(b) $I = 40~W/m^2$
(c) $I = 40~W/m^2$
(d) $I = 10~W/m^2$
Work Step by Step
We can write an expression for the intensity of an electromagnetic wave:
$I = \frac{EB}{2\mu_o} = \frac{E^2}{2\mu_0~c} = \frac{cB^2}{2\mu_0}$
(a) If the amplitude of the electric field is doubled, then the intensity increases by a factor of 4.
$I = 40~W/m^2$
(b) If the amplitude of the magnetic field is doubled, then the intensity increases by a factor of 4.
$I = 40~W/m^2$
(c) If the amplitude of the electric field is doubled and the amplitude of the magnetic field is doubled, then the intensity increases by a factor of 4.
$I = 40~W/m^2$
(d) The intensity does not depend on the frequency.
$I = 10~W/m^2$
