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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Communication System

NTA Abhyas 2020 · Physics · Communication System

In optical communication system operating at 1200 nm, only 2 % of...

In optical communication system operating at 12001200 nm, only 22 % of the source frequency is available for TV transmission having a bandwidth of 5MHz5MHz. The number of TV channels that can be transmitted is

Options

  1. A2 million
  2. B10 million
  3. C0.1 million
  4. D1 million

Correct answer

D. 1 million

Step-by-step solution

The frequency optical communication

v=cλorv=3×1081200×10−9v = \dfrac{c}{\lambda}orv = \dfrac{3 \times {10}^{8}}{1200 \times {10}^{- 9}}

v=25×1013Hzv = 25 \times {10}^{13}Hz

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

v′=2.5×1014×2v^{′} = 2.5 \times {10}^{14} \times 2%

Or v′=2.5×1014×2100v^{′} = 2.5 \times {10}^{14} \times \dfrac{2}{100}

Or v′=5×1012Hzv^{′} = 5 \times {10}^{12}Hz

∴Numberofchannels=v′bandwidth∴ Numberofchannels = \dfrac{v^{′}}{bandwidth}

Or Noofchannels=5×10125×106=106=1millionNoofchannels = \dfrac{{5 \times 10}^{12}}{{5 \times 10}^{6}} = {10}^{6} = 1million
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