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Question: Answered & Verified by Expert
A message signal of $12 \mathrm{kHz}$ and peak voltage $20 \mathrm{~V}$ is used to modulate a carrier wave frequency $12 \mathrm{MHz}$ and peak voltage $30 \mathrm{~V}$. Then, the modulation index is
PhysicsCommunication SystemTS EAMCETTS EAMCET 2016
Options:
  • A 0.32
  • B 6.7
  • C 0.67
  • D 67
Solution:
2328 Upvotes Verified Answer
The correct answer is: 0.67
Given, message signal peak voltage $=20 \mathrm{~V}$
$\therefore \quad E_m=20 \mathrm{~V}$
Carrier voltage, $E_c=30$ volt
Thus, modulation index,
$m_{\mathrm{a}}=\frac{E_m}{E_c}=\frac{20}{30}=\frac{2}{3}=0.67$

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