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 wavelength $\lambda$?

• A. $2.64\text{m}$
• B. $1.25\text{m}$
• C. $3.49\text{m}$
• D. $4.21\text{m}$

Answer 1

The correct option is C $3.49\text{m}$

Comparing the given equation with general form of wave in y - direction,
$E=E_0\cos \left(ky-\omega t\right)$
we get
$k=1.8$
We know that
$k=\frac{2\pi }{\lambda }\lambda =\frac{2\pi }{k}\lambda =\frac{2\pi }{1.8}=3.49\text{m}$