Answer:
The correc answer is c. 128 Hz
Step-by-step explanation:
The lowest resonant frequency of a vibrating object is called the fundamental frequency. Most vibrating objects have more than one resonance frequency. The frequency of the nth mode is n times the frequency of the fundamental mode: fn = n · fo
You know that a column of air in a tube that is open at one end and closed at the other has a frequency of 448 Hz, and the next higher harmonic has a frequency of 576 Hz. So you know that
fn=448 Hz=n*fo (A)
and in the next harmonic fn+1=576 Hz= (n+1)*fo (B)
You can make the difference between (B) and (A):
(B)-(A)
576 Hz - 448 Hz= (n+1)fo - nfo
128 Hz=(n+1-n)fo
128 Hz=fo
So the difference between the frequencies of the two consecutive harmonics is the fundamental frequency of the air column in the tube.