Question

To transmit a signal of $3KHz$ ,frequency the minimum length of antenna is ________ km

• A. $20$
• B. $25$
• C. $50$
• D. $75$

Answer 1

The correct option is B $25$

Wavelength of the signal $\lambda =\frac{c}{\nu }$
$⟹\lambda =\frac{3\times {10}^8}{3\times 1000}={10}^{5}m=100km$
Minimum length of antenna $L=\frac{\lambda }{4}=\frac{100}{4}=25km$
So, option B is correct.