Q160 / 160 · TS EAMCET 2023 (13 May Shift 2) · Physics

A telephonic communication service is working at a carrier frequency of $20 \mathrm{GHz}$. Only $20 \%$ of it is utilized for transmission. If each channel requires a bandwidth of $5 \mathrm{kHz}$, then the number of telephonic channels that can be transmitted simultaneously are

  • A
    $6 \times 10^5$
  • B
    $2 \times 10^5$
  • Correct answer
    C
    $8 \times 10^5$
  • D
    $4 \times 10^5$

Solution

Carrier frequency $=20 \mathrm{GHz}$
$20 \%$ is used in transmission $=\frac{20}{100} \times 20=4 \mathrm{GHz}$
Each channel requires $5 \mathrm{khz}$
$\begin{aligned}<br />& \text {Number of channels }=\frac{4 \times 10^9}{5 \times 10^3} \\<br />& =\frac{4}{5} \times 10^6 \\<br />& =8 \times 10^5<br />\end{aligned}$

Hence, the correct answer is option: 'C'.

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