The method was to fill a container with water and place a long tube inside it.

I am doing a physics experiment and need help finding the speed of sound in air by drawing a line graph.

The method was to fill a container with water and place a long tube inside it. Then using an app on the phone, I had to set different frequencies and place the headphones just outside the top of the tube. I then moved the tube up and down until I heard a resonance. Then recorded the length of the tube out of the water at this point.

I now need to plot a straight line graph and use the gradient in order to work out the speed of sound in air. It is left as an exercise for me to work out what goes on each axis of the graph. Can you please explain how to chose which quantity to place on the x-axis and which quantity you placed on the y-axis to use the final graph to find the speed of sound.

TY :)