A tuning fork A produces 4beats/s with another tuning fork B of frequency 320Hz. On filing one of the prongs of A, 4beats/s is again heard when sounded with the same fork B. Then, the frequency of the fork A before filing is __________
(a) 328Hz
(b) 316Hz
(c) 324Hz
(d) 320Hz
This question was posed to me in examination.
The doubt is from Travelling Waves topic in section Waves of Engineering Physics I