Question

A tube is open at both ends with the air oscillating in the 4th harmonic. How many displacement nodes are located within the tube?

A) 2 

B) 3 

C) 4 

D) 5 

E) 6

Answer 1

The correct option is: (C) 4 

Explanation:

To produce pipe harmonics, the ends are always antinodes. The first (fundamental) harmonic is when there are two antinodes on the end and one node in-between. To move to each next harmonic, add another node in the middle and fill in the necessary antinodes. (ex, 2nd harmonic is ANANA … So the 4^th harmonic would be ANANANANA and have four nodes. Alternative solution … if you know what the harmonics look like you can draw them and manually count the nodes.