Question

A plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is $40 \,MHz$ then its wavelength is

• A. $5\, m$
• B. $7.5\, m$
• C. $8.5 \,m$
• D. $10\, m$

Answer 1

Answer: (B)

$7.5\, m$

Answer 2

Wavelength, $\lambda = \frac{c}{\upsilon} = \frac{3 \,\times\, 10^{8} \,m \,s^{-1}}{40 \,\times \, 10^{6} \,s^{-1}} = 7.5 \,m$