Modern Physics 7 Question 18
18. A $100 V$ carrier wave is made to vary between $160 V$ and 40 $V$ by a modulating signal. What is the modulation index?
(a) 0.4
(b) 0.5
(c) 0.6
(d) 0.3
(Main 2019, 12 Jan I)
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Solution:
- Modulation index is given by
$$ \begin{aligned} \mu & =\frac{A _{\max }-A _{\min }}{A _{\max }+A _{\min }}=\frac{V _{\text {max }}-V _{\text {min }}}{V _{\text {max }}+V _{\text {min }}} \\ & =\frac{160-40}{160+40}=\frac{120}{200}=0.6 \end{aligned} $$
