Question

Two sine waves travel in the same direction in a medium. The amplitude of each wave is A and the phase difference between the two waves is 120°. The resultant amplitude will be

(a) A

(b) 2A

(c) 4A

(d) √2A

Answer 1

The correct answer is (a) A

EXPLANATION:  

The resultant amplitude  

y = A sin(⍵t-kx) + A sin(⍵t-kx+120°)  

 →y = 2A Sin(⍵t-kx+60°)*cos60°   

→y = A sin(⍵t-kx+60°)    

 Hence the resultant amplitude is A.