A carrier is simultaneously modulated by two sine waves

A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4, the total modulation index—

1. is 1
2. cannot be calculated unless the phase relations are known
3. is 0.5
4. is 0.7

Given μ₁ = 0·3, μ₂ = 0·4
μ_eff = √μ₁² + μ₂²
= √(0.3)² + (0.4)²
= √0.09 + 0.16
= √0.25
= 0.5