Question

two turning forks have the same amplitude but diffrerent frequency. at the same time produce a comx wave . what is tthis called ?

if the period of the compelx wave that produce 0.25s and the period of one of the turning fork is 0.04s what is one possible frequency of the other turning fork ?

when the sinusoidal waves from the tuning forks are in opposite phases, what happens at those points to the complex wave they produce ?  

Answer 1

In the case of two tuning forks have same aplitude and different frequency at same time, the resultant successive maxima (waxing)and minima (wanning) of sound obtained. This complex effect produces beats. Here, the rise of intensity called waxing of sound and fall is called wanning of sound. Here, the beat frequency is called the successive difference between the frequencies emitting from turning forks.

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Frequency correspoinding to T = 0.25 is  

f = 1 /T = 1/ 0.25 = 4 Hz

Means it produces 4 Hz, 8 Hz, 12, Hz.....in successive time periods

Frequency correspoinding to T = 0.04 is  

   f '= 1 /T' = 1/ 0.04 = 25 Hz

Means it produces 25 Hz, 50 Hz, 75, Hz, 100 Hz.....in successive time periods

The possible frequency of other coicide the first one is 4 x 25 = 100 Hz

( take least common factor of 4 Hz and 25 Hz )

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If two sine waves are superimpose in opposite direction, standing waves are created.  when waves out of phase, then they cancel, no waves is produced. When they superimpose in phase they added together. When two sine waves pass through each, net result alternates between zero and some maximum amplitude. This pattern does not moves, it oscillates; called standing wave.