Wave speed = wavelength * frequency

[Addallat]

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If a wave moves into another medium does the wavelength change?

In my notes i have written down that when a wave moves into another medium wave speed will change and frequency will stay the same

 

[knower214]

The wavelength will change, if a wave moves into another medium. This will cause the velocity to change, but the frequency will still the same. Because the frequency of the sound is based upon the source of the wave, while the wavelength is based upon the medium of propagation.

The frequency will change only when the sender/receiver is moving relative to one another. (Doppler Effect)

 

[gettheleadout]

Yep, wavelength and velocity can and do change, frequency of an already-propagating wave cannot.

 

[GomerPyle]

Yep, wavelength and velocity can and do change, frequency of an already-propagating wave cannot.

This includes both sound and light waves, correct? Once the sound/light wave is formed, the frequency is fixed. When they change medium, light travels slower in more dense medium and sound travels in more dense medium (unless it is a gas, which then it travels faster in less dense, hotter gas)?

 

[gettheleadout]

This includes both sound and light waves, correct? Once the sound/light wave is formed, the frequency is fixed. When they change medium, light travels slower in more dense medium and sound travels faster in more dense medium (unless it is a gas, which then it travels faster in less dense, hotter gas)?

You accidentally a word, but yes that's all correct haha

 

[GomerPyle]

You accidentally a word, but yes that's all correct haha

Haha thanks 🙂

 

[dudewheresmymd]

Yep, wavelength and velocity can and do change, frequency of an already-propagating wave cannot.

is this true for both light and sound waves?

 

[siffster]

For light: Frequency stays the same. If c=lambda*f, increasing the speed of light increases the wavelength or vice versa. As you go into a medium with a higher index of refraction(= speed of light is slower than in vacuum), speed of light decreases, so the wavelength will decrease.

For sound: Frequency stays the same. v=lambda*f. Going from a gas to a liquid to solid phase increases the speed of sound, which is due to the elastic properties of the medium(there is a bigger restoring force for each molecule as you go from gas to solid. Think of F=-kx with a solid having the highest k-value). Therefore, as you increase the speed of sound, you increase the wavelength