# What happens to wavelength as temperature of air increases?

• turtlepower
In summary, CWatters says that the speed of sound in air increases with temperature, and that the wavelength must increase to balance the equation.
turtlepower

## Homework Statement

what happens to wavelength if temperature increases?

## Homework Equations

V= lambda * frequency

## The Attempt at a Solution

I'm guessing since no change to frequency is stated?.. and I know that the speed of sound increases as temperature increase. The wavelength would have to increase in order to balance the equation V= lambda * frequency?
But I'm not sure if it's correct or why and if frequency would be affected by temperature or not..
I can't find a straight answer or explanation on google so here I am.

The molecules vibrate faster at higher temperature.
\
Temperature is defined as a measure of the average random motion of particles within a system.

Last edited:
turtlepower said:
But I'm not sure if it's correct or why and if frequency would be affected by temperature or not..

Does the source of the sound (eg a signal generator driving a loudspeaker) change frequency when the temperature changes?

Hi turtlepower, Welcome to Physics Forums.

Please try to make your Problem Statement self complete; helpers should be able to understand the complete problem by reading the problem statement alone. For example, it should state clearly that the problem pertains to sound in air.

turtlepower said:
I'm guessing since no change to frequency is stated?.. and I know that the speed of sound increases as temperature increase. The wavelength would have to increase in order to balance the equation V= lambda * frequency?
But I'm not sure if it's correct or why and if frequency would be affected by temperature or not..
Those are good ideas. You should be able to find a source to confirm that the speed of sound in air (or any gas) varies with temperature. A web search should turn up a relevant equation (for example, the Hyperphysics web page on Sound Speed in Gases). You should also be able to make an argument about the frequency being constant -- think of how a given sound is projected into the air to begin with. Must the mechanism that produces the sound waves be tied to the temperature?

Edit: Ah. I see that CWatters got there ahead of me!

## 1. What is the relationship between air temperature and wavelength?

The relationship between air temperature and wavelength is an inverse relationship. This means that as the temperature of air increases, the wavelength decreases, and vice versa. This is known as Wien's displacement law.

## 2. Why does the wavelength change as air temperature increases?

The wavelength changes as air temperature increases because of the effect of thermal energy on the motion of air molecules. As the temperature increases, the air molecules move faster and this leads to a decrease in the wavelength of the light passing through the air.

## 3. How does humidity affect the relationship between air temperature and wavelength?

Humidity has a minimal effect on the relationship between air temperature and wavelength. However, high humidity can slightly increase the wavelength of light passing through air due to the presence of water vapor molecules, which can absorb some of the thermal energy and slow down the movement of air molecules.

## 4. What is the impact of air pressure on the wavelength of light passing through air?

Air pressure has a negligible effect on the wavelength of light passing through air. The relationship between air temperature and wavelength remains the same regardless of the air pressure.

## 5. Can the change in wavelength due to air temperature be measured?

Yes, the change in wavelength due to air temperature can be measured using instruments such as a spectrophotometer or a spectrometer. These instruments can detect even small changes in wavelength and can be used to study the relationship between air temperature and wavelength.

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