A student in her physics lab measures the standing-wave modes of a tube. The lowest frequency that makes a resonance is 20 Hz. As the frequency is increased, the next resonance is at 60 Hz. What will be the next resonance after this?

A. 80 Hz

B. 100 Hz

C. 120 Hz

D. 180 Hz

Answer: B. 100 Hz

Explanation:

Here, the frequency for the standing-wave modes of a tube is given as

f (n) = m*f

For first frequency put f = 20 Hz, m=1

So f₁ = 1*20 = 20Hz

The next resonance occurs at m=3

f₂ = 3*20 = 60 Hz

So meaning at odd intervals the resonance occurs so next will occur at m=5

So,

f₃ = 5*20 = 100 Hz

So, option B. 100 Hz is correct.