Multiple ! ! 1.) four beats per second are heard when an unknown tuning fork and a 240 hz tuning fork are struck simultaneously. select the two possible frequencies of the tuning fork. 240 hz 236 hz 244 hz 238 hz 2.) four beats per second are heard when an unknown tuning fork and a 240 hz tuning fork are struck simultaneously. this same unknown tuning fork and a 250 hz tuning fork are struck. six beats are heard. its exact frequency: is 256 hz is 236 hz is 244 hz cannot be determined

1) The beat frequency related to the interference between two waves is given by

where  is the beat frequency, and  and  are the frequencies of the two waves.

In our problem ,the beat frequency is , and one of the two frequencies is , so the frequency of the unknown tuning fork can be:



2) Given the previous problem, the frequency of the unknown tuning fork can be either 236 Hz or 244 Hz. When this unknown fork is struck with another fork of 250 Hz, the beat frequency is 6 Hz. Therefore, the only possibility is that the frequency of the first tuning fork is 244 Hz; in fact, we have: