Question

A radio can tune to any station in $7.5MHz$ to $12MHz$ band. The corresponding wavelength band is

• A. $40mto25m$
• B. $30mto25m$
• C. $25mto10m$
• D. $10mto5m$

Answer 1

The correct option is A $40mto25m$

We know for a wave:
Velocity, $v=f\lambda$

where $v$ is the velocity of the wave, $f$ is the frequency and $\lambda$ is the wavelength.

For radio waves

Speed of light, $v=c=3\times {10}^{8}m/s$

Upper limit:-

$c=f_1{\lambda }_1$

${\lambda }_1=\frac{3\times {10}^8}{7.5\times {10}^6}$

${\lambda }_1=40m$

Lower limit :-

$c=f_2{\lambda }_2$

${\lambda }_2=\frac{3\times {10}^8}{12\times {10}^6}$

${\lambda }_2=25m$

Therefore, the corresponding wavelength band is $40m$ to $25m$

Option $\left(A\right)$ is correct.