Question
S 1 and S 2 are two identical sound sources of frequency 656   Hz . The source S 1 is located at O and S 2 moves anti-clockwise with a uniform speed 4 2   m   s - 1 on a circular path around O , as shown in the figure. There are three points P ,   Q and R on this path such that P and R are diametrically opposite while Q is equidistant from them. A sound detector is placed at point P . The source S 1 can move along direction O P . [Given: The speed of sound in air is 324   m   s − 1 ] Consider both sources emitting sound. When S 2 is at R and S 1 approaches the detector with a speed 4   m   s - 1 , the beat frequency measured by the detector is _____ Hz .