Question

Two longitudinal waves: s1 = 3cos(11t) & s2 = 3cos(10t) interfere. What is the amplitude of the resulting wave?

(a) 6cos(0.5t)

(b) 6sin(0.5t)

(c) 6cos(10.5t)

(d) 6sin(10.5t)

The question was posed to me in semester exam.

I'd like to ask this question from Waves in section Waves of Physics – Class 11

Answer 1

Right choice is (a) 6cos(0.5t)

Easiest explanation: s = s1+s2 = 2(3)*cos(1/2)t*cos(21/2)t

= 6cos(0.5t)cos(10.5t).

The term 6cos(0.5t) corresponds to the amplitude.