The maximum and minimum amplitudes of a modulated carrier wave are 1000 mV and 200 mV respectively, the modulation index is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( \displaystyle\frac{2}{3} \)
In amplitude modulation the amplitude of the carrier \( A_c \) varies between \( A_c + A_m \) and \( A_c - A_m \), where \( A_m \) is the amplitude of the message signal. The modulation index is \( \mu = A_m/A_c \).
\( A_{\max} = A_c + A_m \)
\( A_{\min} = A_c - A_m \)
\( \displaystyle \mu = \frac{A_m}{A_c} = \frac{A_{\max} - A_{\min}}{A_{\max} + A_{\min}} \)
\( \displaystyle \mu = \frac{1000 - 200}{1000 + 200} = \frac{800}{1200} = \frac{2}{3} \)
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):
Exercises – …
