Question

As the value of the modulation index increases, 

(1) Amplitude of the central band increases 

(2) Amplitude of the central band decreases 

(3) Total power carried by the sidebands increases 

(4) Total power carried by the sidebands decreases

Answer 1

Correct option: (3) Total power carried by the sidebands increases

Explanation: 

Amplitude of the central band is independent of the modulation index. 

Fraction of total power carried by the central carrier wave = 2/2+m² 

Fraction of total power carried by the sidebands = m²/2+m² 

Therefore, as the modulation index increases, the useful power carried by the central band decreases, but the carried by the sidebands increases.