Modern Physics 7 Question 28

29. In communication system, only one percent frequency of signal of wavelength 800nm can be used as bandwidth. How many channal of 6MHz bandwidth can be broadcast this? (c=3×108m/s,h=6.6×1034Js)

(Main 2019, 9 Jan II)

(a) 3.75×106

(b) 3.86×106

(c) 6.25×105

(d) 4.87×105

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Solution:

  1. Here,

Signal wavelength, λ=800nm=8×107m

Frequency of source is

 As, f=cλ=3×1088×107=3.75×1014Hz

Total bandwidth used for communication

=1=3.75×1012Hz

So, number of channel for signals = total bandwidth available for communication 

bandwidth of TV signal

=3.75×10126×106=0.625×106=6.25×105



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