The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by
$B = 1.2 \times 10 ^ { - 6 } \sin \left[ 2 \pi \left( \frac { z } { 240 } - \frac { t \times 10 ^ { 7 } } { 8 } \right) \right]$
in SI units.What is the frequency of the wave?
A)500 MHz
B)250 kHz
C)1.25 MHz
D)10 mHz
E)300 MHz

Question

The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by 
$B = 1.2 \times 10 ^ { - 6 } \sin \left[ 2 \pi \left( \frac { z } { 240 } - \frac { t \times 10 ^ { 7 } } { 8 } \right) \right]$ 
in SI units.What is the frequency of the wave?
A)500 MHz
B)250 kHz
C)1.25 MHz
D)10 mHz
E)300 MHz

Quizplus · Accepted Answer

The angular frequency $\omega$ is given by $2\pi \times \text{frequency}$. From the equation, $\omega = \frac{2\pi \times 10^7}{8}$. Solving for frequency gives $1.25 \times 10^6$ Hz or 1.25 MHz.

The Magnetic Field of a Plane-Polarized Electromagnetic Wave Moving in the Z-Direction