Harmonics terminology for an open-closed tube

[jumbogala]

Homework Statement

When you have an open-closed tube, I was taught in high school that when using the equation

λ = 4L/m, m = 1, 3, 5, 7, ... where m = 1 corresponds to the fundamental mode.

I was taught that m = 1 is the 1st harmonic, m = 3 is the 3rd harmonic, etc.

But my physics prof says m = 1 is the 1st harmonic, m = 3 is the 2nd, m = 5 is the 3rd, and so on. I'm just really confused about which one is right... can anyone explain?

Homework Equations

The Attempt at a Solution

 

[satxer]

m=3 is the second harmonic because when m=2 then it's a closed tube.