Question

Choose the correct answer from the alternatives given.
A plane electromagnetic wave travel in vacuum along z-direction. If the frequency of the wave is 40 MHz then its wavelength is then

• A. 5 m
• B. 7.5 m
• C. 8.5 m
• D. 10 m

Answer 1

Answer: (B)

7.5 m

Given: The frequency of the electromagnetic wave is $40MHz$.

To find: The wavelength of the electromagnetic wave in vacuum.

The wavelength of the electromagnetic wave is given by:

Wavelength, $\lambda =\frac{c}{\nu }$

$\Rightarrow \frac{3\times {10}^{8}m/s}{40\times {10}^6{s}^{-1}}=7.5m$

So, option $\left(B\right)$ is correct.