question_answer

s Two point sources, which are in phase and separated by distance\[D=15\lambda \], emit identical sound waves of wavelength\[\lambda \]. If a circle with a radius much greater than D, centered on the mid-point between the sources. What is the number of points around the circle at which the interference is fully constructed?

A)  2                            

B)  4

C)  6                                            

D)  8

Correct Answer: B

Solution :

 Idea This question is based on the concept of constructive and destructive interference of waves and its relation with path difference. At point P and Q path difference is equal to zero. So, point P and Q are parts y constructive interference, Now in points R and S path difference is equal to 1.5\[\lambda \], according to question path difference of 1.5\[\lambda \]also correspond, to point of constructive difference. So, P, Q, R, and S are 4 points around circle and are in constructive interference. TEST Edge Questions based on phase difference, path difference, constructive interference and destructive interference are frequently asked.