# Sound Waves and hertz

1. Apr 23, 2006

### brokentruce

i really had troubles with solving this problem and it would be greatly appreciated if i can get a full solution, thank you

A vibrating 400.0 Hz tuning fork is placed in fresh water. What is the frequency in hertz and the wavelength in metres.

a) within the water at 25 C
b) when the sound waves move into the air at 25 C?

2. Apr 23, 2006

### nrqed

The frequency will be the same no matter the medium. For the wavelength, you must have seen $\lambda = v/f$ so you need to know the speed of sound in the medium you are considering. You must have the values somewhere in your book or notes.

3. Apr 23, 2006

### Hootenanny

Staff Emeritus
I'm afraid we do not give full solutions here. However, if you would like to post your work, we will be more than happy to guide you to the correct answer.

~H

4. Apr 23, 2006

### brokentruce

1493 m/s is the speed for sounds iin water at 25 C
332 m/s is the speed for sounds in air at 0 C

So like i kno how to get the wavelength the only this thats throwing me off is that the frequency might be different although theoretically freqeuncy can only be changed from its source

5. Apr 23, 2006

### Hootenanny

Staff Emeritus
You are correct. You will need to correct your velocity in air though.

~H

6. Apr 23, 2006

### nrqed

As Hoot said, you should always include some of your work with your question. I answered because it was a simple question but I should have asked to see what you had tried first (this is to avoid having people come here to get their homework done without trying first).

You are correct, the frequency is fixed by the source. That does not depend on the medium. For the wavelength, I gave the formula (which hopefully you recognize!!)

7. Apr 23, 2006

### brokentruce

so leave the frequencies to be the same but just solve for the wavelength .............if so..........THANK YOU SOOOOOOO MUCH this really helped

8. Apr 23, 2006

### brokentruce

Sorry i am new to this, ill remember to abide by the rules the next time, wasnt aware of them

9. Apr 23, 2006

### Hootenanny

Staff Emeritus
Don't forget to correct your velocity for air though!

~H

10. Apr 23, 2006

### brokentruce

the speed is correct infact because thats what the table in my book has.......maybe u think that speed is at 0 C but is is in fact in 25 C

11. Apr 23, 2006

### Hootenanny

Staff Emeritus
The speed of sound is 346.3 m/s in air at 25oC.

~H

12. Apr 23, 2006

### nrqed

No problem..and welcome!

Hoot wanted to make sure that you would use the speed in air at 25 C because in your post you quoted the value at 0 C.

good luck!