# Sound And Waves

1. Feb 2, 2005

### Markd

Hi,

I am having problems with 2 sound related questions

1) While diving you make a loud clank with your oxygen tanks on a rock, how far away are you from the nearest underwater reflecting surface if the sound returns to you in 3.00s (assume the speed of sound in water to be 1440m/s)

2) A tuning fork with a frequency of 324Hz is held over a tube whose length can be changed by raising and lowering a column of water in the tube. The surface of the water, initially very near to the top of the tube is gradually lowered if the speed of sound in air is 336m/s how far from the top of the tube is the surface of the water when the first point of constructive interference is detected

I really did try to figure them out but must be missing something any hints?

2. Feb 2, 2005

### HallsofIvy

Staff Emeritus
Well that's pretty easy isn't it? the sound has to travel to the "reflecting surface" and then back again in 3 seconds. How far can sound travel in 3 seconds? What is half of that?

If the frequency is 324 waves per second and the speed is 336 m/s, how long is one wave? Since a "node" occurs at the midpoint of a wave, how long can the distance from one node to another be?

3. Feb 2, 2005

### Markd

Great thanks!

It was the "node" part of the question that confused me =/