Question

An antenna uses electromagnetic waves of frequency 5 MHz. For proper working, the size of the antenna should be

• A. 15 km
• B. 15 m
• C. 3 km
• D. 300 m

Answer 1

Answer: (B)

$C=f\lambda$
$\lambda =\frac{C}{f}=\frac{3\times 10^8}{5\times 10^6}=10^2=60m$
The antenna length should be $\frac{\lambda }{4}=\frac{60}{4}=15m$