Question

A plane electromagnetic wave of frequency $40\text{MHz}$ travels in free space in the X - direction. At some point and at some instant, the electric field $\overrightarrow{E}$ has its maximum value of $750\text{N/C}$ in Y -direction. The wavelength of the wave is-

• A. $3.5\text{m}$
• B. $5.5\text{m}$
• C. $7.5\text{m}$
• D. $9.5\text{m}$

Answer 1

The correct option is C $7.5\text{m}$

$f=\frac{C}{\lambda };\lambda =\frac{C}{f}=\frac{3\times {10}^8}{40\times {10}^6}=7.5\text{m}$