Q18 / 32 · NTA Abhyas (JEE Main) 2020 · Physics · Communication System

In optical communication systems operating at 1200 nm, only 2% of the source frequency is available for TV transmission having a bandwidth of 5 MHz. The number of TV channels that can be transmitted is 10n. The value of n is

Correct answer: 6

Solution

The frequency of optical communication is given by,

v=cλ or v=3×1081200×10-9

v=25×1013 Hz

But only 2% of the source frequency is available for TV transmission.

v′=2.5×1014 ×2%

v′=2.5×1014 ×2100

v′=5×1012 Hz

∴  Number of channels=v′bandwidth

No of channels=5×10125×106=106=1 million

Hence, the correct answer is 6.

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