Which of the following scenarios describes a condition in which resonance can occur?

a. two tuning forks that vibrate at the same frequency are near each other. one tuning fork is struck with a mallet so that it vibrates.
b. two tuning forks are struck simultaneously, one with a frequency of 659hz and one with a frequency of 639 hz, causing beats.
c. a tuning fork is over a column of air that is 9/2 the wavelength of the wave produced by the tuning fork.
d. an isolated tuning fork is struck with a mallet, causing it to vibrate strongly at 659 hz.

C. A tuning fork is over a column of air that is 9/2 the wavelength of the wave produced by the tuning fork.

Explanation:

As we know that the frequency in the air column is given by

now we know that the length of air column is L then at the condition of resonance we have

so here at the condition of resonance the length will be integral multiple of half of the wavelength.

So here for N = 9 we have

so here correct answer will be

C. A tuning fork is over a column of air that is 9/2 the wavelength of the wave produced by the tuning fork.

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