A long air column is closed at one end and open at the other

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

0.90\,\text{m}

long air column is closed at one end and open at the other. A probe microphone detects pressure nodes at positions

0.10\,\text{m}

and

0.30\,\text{m}

from the closed end, with no additional nodes between these two points. Which harmonic of the column is being excited? (a)

5^{\text{th}}

harmonic (b)

9^{\text{th}}

harmonic (c)

7^{\text{th}}

harmonic (d)

11^{\text{th}}

harmonic