Interference occurs with not only light waves but also all frequencies of electr

Question

Interference occurs with not only light waves but also all frequencies of electromagnetic waves and all other types of waves, such as sound and water waves. Suppose that your physics professor sets up two sound speakers in the front of your classroom and uses an electronic oscillator to produce sound waves of a single frequency. When she turns the oscillator on (take this to be its original setting), you and many students hear a loud tone while other students hear nothing.

The professor adjusts the oscillator to produce sound waves of twice the original frequency. What happens? (This is a multiple choice question)

A: The students who originally heard a loud tone now hear nothing, and the students who originally heard nothing now hear a loud tone.

B: The students who originally heard a loud tone again hear a loud tone, and the students who originally heard nothing still hear nothing.

C: Among the students who originally heard nothing, some still hear nothing but others now hear a loud tone.

D: Some of the students who originally heard a loud tone again hear a loud tone, but others in that group now hear nothing

Explanation / Answer

The distance from center of two speakers to the point where there will be maximum intensity is given by

y=mwD/d where, m is just an integer, w is wavelength, D is distance of students from speakers, d is distance between speakers.

v=uw, u is frequency, v is speed of propagation of wave. So, u=v/w.

Hence y= mvD/ud.

Therefore if frequency is increased, distance of maximum sound will decrease, hence some other students will hear maximum sound.

Student who originally gear nothing, some of them will hear, and some will not.

This is multiple correct answer.

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