Q 12-08-149JEE MainJEE Main 2021 (27 Jul, Shift 1)Easy
The amplitude of upper and lower side bands of AM wave where a carrier signal with frequency $11.21$ MHz, peak voltage $15$ V is amplitude modulated by a $7.7$ kHz sine wave of $5$ V amplitude are $\dfrac{a}{10}$ V and $\dfrac{b}{10}$ V respectively. Then the value of $\dfrac ab$ is ______.
Numerical value type. Enter your answer.
Answer: 1
Modulation index $\mu = \dfrac{A_m}{A_c} = \dfrac{5}{15} = \dfrac13$.
Each side band has amplitude $\dfrac{\mu A_c}{2} = \dfrac{A_m}{2} = 2.5$ V, so $a = b = 25$ and $\dfrac ab = 1$.
Solution by Sreeraj P, M.Sc Physics