The sound produced by a tuning fork is a/an .....

$A$ telephonic communication service is working at a carrier frequency of $10 \ GHz$. Only $10\%$ of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of $5 \ kHz$?

If the length of an antenna is $150 \,cm$,the transmission frequency is . . . . . . $MHz$. (Speed of light in vacuum $= 3 \times 10^8 \,ms^{-1}$)

Frequencies in the $UHF$ range normally propagate by means of:

The amplitude of the upper and lower sidebands of an $A.M.$ wave,where a carrier signal with frequency $11.21 \, MHz$ and peak voltage $15 \, V$ is amplitude modulated by a $7.7 \, kHz$ sine wave of $5 \, V$ amplitude,are $\frac{a}{10} \, V$ and $\frac{b}{10} \, V$ respectively. Then the value of $\frac{a}{b}$ is $....$

$A$ signal of frequency $10 kHz$ and peak voltage $10 V$ is used to amplitude modulate a carrier of frequency $1 MHz$ and peak voltage $20 V$. The side-band frequencies in $kHz$ are