QJEEM18Ph9bda: JEE Main 2018 Physics - Class 12 JEEM18Ph9bda Solution: A telephonic communication service is working at carrier…

The carrier frequency is 10 GHz, and only 10% of it is utilized for transmission. Therefore, the bandwidth used for transmission is:

$\text{Bandwidth} = 10\% \times 10 \text{ GHz} = 0.1 \times 10 \text{ GHz} = 1 \text{ GHz}$

We should convert this to kHz because the channel bandwidth is given in kHz:

$1 \text{ GHz} = 1,000,000 \text{ kHz}$

Now, if each telephonic channel requires a bandwidth of 5 kHz, the number of channels that can be transmitted simultaneously is:

$\text{Number of channels} = \frac{\text{Total bandwidth}}{\text{Bandwidth per channel}}$

$\text{Number of channels} = \frac{1,000,000 \text{ kHz}}{5 \text{ kHz}}$

$\text{Number of channels} = 200,000$

So, 200,000 telephonic channels can be transmitted simultaneously.

Among the given options, the correct answer is Option C: $2 \times 10^5$ .