Question

Suppose that the electromagnetic wave in vacuum is
$\overrightarrow{E}=\{\left(3.1\frac{N}{C}\right)\cos \left[(1.8\frac{rad}{m}\right)y+(5.4\times {10}^6\frac{rad}{s})t]\hat{i}$
What is the frequency?

• A. $8.6\times {10}^{5}Hz$
• B. $4.3\times {10}^{5}Hz$
• C. $8.6\times {10}^{3}Hz$
• D. $4.3\times {10}^{3}Hz$

Answer 1

The correct option is A $8.6\times {10}^{5}Hz$

Comparing the given equation with general form of wave equation
$E=E_0\cos \left(ky-\omega t\right)$
we get
$\omega =5.4\times {10}^6\text{rad/s}$
We know that frequency is given by
$\nu =\frac{\omega }{2\pi }$
Putting value of $\omega$ and solving we get
$\nu =8.6\times {10}^5\text{Hz}$