An AM modulator has output xc (t) = 40 cos 400 πt + 4 cos

An AM modulator has output x_c (t) = 40 cos 400 πt + 4 cos 360 πt + 4 cos 440 πt The AM modulation efficiency is—

The given modulator output
x_c(t) = 40 cos 400 πt + 4 cos 360 πt + 4 cos 440πt x_c(t) may be written as

x_c(t) = 40		1 +	1	cos40πt		cos400πt
			5

...(1)
On comparing equation (1) with standard equation
x_c(t )= A_c (1 + μ cos ω_mt) cos ω_ct

μ =	1	,A_c = 40
	5

Efficiency =	μ²	=		(1/5)²		=	1/25	=	1
	2 + μ²			2 + (1/5)²			50 + 1/25		51

= 0.02
Hence alternative (B) is correct choice.