# Resonance (standing waves) in glass tube with water

• cheff3r
In summary, the conversation discusses how to find the position of resonance in a vertical glass tube with a length of 1m and a tuning fork vibrating at 660 Hz. The equation for calculating the position is incorrect and should be replaced with the formula: L=n*λ/4, where n is an odd number and λ is the wavelength. The correct wavelength for a 660 Hz sound wave is 0.5m and the first resonance for a closed pipe is at the quarter wave position.
cheff3r

## Homework Statement

The water level in a vertical glass tube (length 1 m) can be adjusted to any position in the tube. A tunning fork vibrating at 660 Hz is held just over the open end of the tube. calculate at what position of the water level will there be resonance (standing waves) in the tube? Assume speed of sound is 330 m/s

## Homework Equations

f=n*v/(4*L) where n is an odd number
I'm guessing I've gone wrong with relevant equations part

## The Attempt at a Solution

My fist assumption is that the end with water in it should be considered to be closed even though in reality some sound would go through the water, is this correct? or should i be treating it like the one on this site http://hyperphysics.phy-astr.gsu.edu/hbase/Class/PhSciLab/restube2.html
anyway so treating it as closed i can use the above formula re-arranged or length
L=4*f/(n*v)
n=1: L = 4*660/(1*330) = 8 m
n=3: L = 4*660/(3*330) = 24 m
n=5: L = 4*660/(5*330) = 40 m clearly all are going to be to big for tube, i also considered different frequencies with no success, it is unlikely my lecture would give a trick question, am i doing something wrong?

If it helps you can ignore the link, only have to treat the water as closed end, the only problem is the above is still wrong (teacher gave us a hint).
I don't understand what I'm doing wrong I believe its the right formula and also the right method am I stuffing up units?

The speed of sound is 340 m / sec

What is the wavelength of a 660 Hz sound wave ?

What length is one quarter of this?

165 Hz giving
L=4*f/(n*v)
n=1: L = 4*165/(1*340) = 1.9 m
n=3: L = 4*165/(3*340) = .647 m
n=5: L = 4*165/(5*340) = 0.388 m
which is in the right area
but don't i want resonate frequency which would be a full oscillation?

Or another question is what made you choose to divide by 4? (want to learn a method so I can do future questions)

Wavelength is = speed of sound in air (330 m/sec) / frequency ( 660 Hz) = answer in meters.

I get 0.5 meters as the wavelength, but check it.

The first resonance for a closed pipe is at the quarter wave position. One quarter of 0.500 M is 0.125 M. This is about 5 inches. Subsequent resonances are at three times this, five times this, etc.

Those formulas you quoted seem to be totally wrong. You do not need to use them anyway.

Last edited:
Ah thank you so much its is 0.5 meter wave length, that formula is wrong (my fault) and now I get the right sort of answers being 0.125, 0.375, 0.625 and 0.875 m
thanks again

Last edited:

## 1. What is resonance in a glass tube with water?

Resonance refers to a phenomenon where an object vibrates at its natural frequency when exposed to an external force. In a glass tube with water, resonance occurs when sound waves are produced and reflected back and forth between the two ends of the tube, creating standing waves.

## 2. How does the length of the glass tube affect resonance?

The length of the glass tube is directly related to the wavelength of the sound waves produced. When the length of the tube is equal to half the wavelength, resonance occurs. This is known as the fundamental frequency. Changing the length of the tube will result in a change in the frequency and the standing wave pattern formed.

## 3. Why does the water level in the tube affect resonance?

The water level in the tube acts as a variable for changing the length of the tube. As the water level is adjusted, the length of the tube changes, altering the frequency of the standing waves and thus affecting the resonance. The water level also determines the number of antinodes (points of maximum amplitude) in the standing wave pattern.

## 4. What factors can affect the resonance in a glass tube with water?

The resonance in a glass tube with water can be affected by various factors such as the diameter of the tube, the type of liquid used, the temperature of the liquid, and the material of the tube. These factors can alter the speed of sound and thus change the frequency and wavelength of the standing waves.

## 5. What is the significance of studying resonance in a glass tube with water?

Studying resonance in a glass tube with water has practical applications in various fields such as acoustics, music, and engineering. It helps in understanding the behavior of sound waves and their interactions with different mediums. It also has educational value in demonstrating the principles of physics and wave phenomena.

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