Wave frequency, medium and temperature

[latot]

Hi hi, I'm looking into how temperature affects waves, but I don't know too much about this, in how temperature mixes with all of this, I have this questions:

We have a particle vibrating at frequency $f$ at a certain temperature $t_p$, and a medium with other temperature $t_m1$.

If the generated wave move to the same medium but with other temperature $t_m2$?

How can we write the generated wave in function of $f$, $t_p$ and $t_m1$? (with and without exchange of heat).

I would like consider 2 cases, where the particle is vibrating without a external force, and with a external force (in one the kinetic energy is used to generate the waves, in other the kinetic energy is just constant, or something supply the difference to keep the particle vibrating at the same frequency and amplitude).

There is a lot of ways to mix this, but let's start with this.

Thx.

 

[berkeman]

What kind of waves? EM waves, sound waves in liquid/solid, etc.?

 

[Drakkith]

Hi hi, I'm looking into how temperature affects waves, but I don't know too much about this, in how temperature mixes with all of this

The answer is complicated, as it depends on the type of wave and the type of medium. The short answer is that temperature generally affects waves by changing the density of the medium they are traveling through. For light, this usually means a reduction in density as temperature increases, which means a decrease in refractive index. However, some materials do the opposite. I can't give an example off the top of my head though.

 

[jbriggs444]

The answer is complicated, as it depends on the type of wave and the type of medium. The short answer is that temperature generally affects waves by changing the density of the medium they are traveling through. For light, this usually means a reduction in density as temperature increases, which means a decrease in refractive index. However, some materials do the opposite. I can't give an example off the top of my head though.

In air (or an ideal gas), increasing temperature decreases density without changing the bulk modulus, so the speed of sound increases with increasing temperature. http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/souspe3.html

In at least some metals, the material gets softer with increasing temperature so the speed of sound decreases with increasing temperature. The first reference I Googled up was https://link.springer.com/article/10.1007/s10765-009-0683-2 "The longitudinal wave velocity in X14CrMoS17 steel varies from 6,002 m·s−1 at 293 K to 5,115 m·s−1 at 1,173 K"

 

[latot]

:O Ty.

Lets think in waves of sound and light.

I would like if there is some formulations for this, how is constructed the wave equation when there is heat in the middle?

Is right, if we increase the heat we will down the density, but only if there is space to expand it, but if there is no space, how will travel the wave?

 

[jbriggs444]

Is right, if we increase the heat we will down the density, but only if there is space to expand it, but if there is no space, how will travel the wave?

Nothing is perfectly rigid. Especially not when considering sound waves. Even if there is no space to expand into at the ends, the jello in the middle can still jiggle around.

If you are asking about how the speed of sound varies in hot, high pressure material versus cold, low pressure material, the answer is that I don't know.

However, since the speed of sound varies with density and the bulk modulus, and since you are now holding density constant, that narrows the scope of your investigation pretty well.

Edit: Google is your friend, e.g.

https://nvlpubs.nist.gov/nistpubs/jres/77A/jresv77An6p755_A1b.pdf "The Effect of Temperature and Pressure on the Refractive Index of Some Oxide Glasses"