Question

TV waves have a wavelength range of $1-10\text{metre}$, their frequency range ( in $MHz$) is

• A. $300-3000$
• B. $3-3000$
• C. $30-3000$
• D. $30-300$

Answer 1

The correct option is D

$30-300$

Step 1: Given

$c=3\times {10}^{5}km/s=3\times {10}^{8}m/s$

${\lambda }_1=1m$

${\lambda }_2=100m$.

Step 2: Calculating frequency

We know that relation between frequency, wavelength and velocity of waves$f=\frac{c}{\lambda }$.

Therefore, $f_1=\frac{c}{\lambda }=\frac{3\times {10}^8}{1}=3\times {10}^{8}Hz=300MHz$

$f_2=\frac{c}{\lambda }=\frac{3\times {10}^8}{10}=3\times {10}^{7}Hz=30MHz$

Therefore, frequency range is between $30MHz$to$300MHz$.

Therefore, correct option is (d) $30-300$.