For an audio signal of amplitude 0.1 V, used in amplitude modulation of a carrier wave of amplitude 0.2 V, the modulation index would be:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 0.5
The modulation index is the ratio of the amplitude of the modulating (audio) signal to that of the carrier.
\( \displaystyle \mu = \frac{A_m}{A_c} = \frac{0.1\,\mathrm{V}}{0.2\,\mathrm{V}} = 0.5 \)
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Amplitude Modulation – …
