How Does Temperature Affect Electromagnetic Waves?

[jainabhs]

What exactly is tempertaure?
As far as I know it represents the average vibration of atoms.
How it relates to EM wave? because I have read in many Physics texts saying that 'the temperature of this wave is X Kelvin'. How do they find the temperature of individual EM wave?

Correct me if I am wrong for following:
Suppose an aluminium rod and wood are at room temperature;In case of Aluminium rod the atoms as well as free electrons would contribute to its temperature. For wood I think only the atoms will contribute.

 

[f95toli]

How it relates to EM wave? because I have read in many Physics texts saying that 'the temperature of this wave is X Kelvin'. How do they find the temperature of individual EM wave?

It is not really the temperature of the EM wave. "Temperature" can here mean one of two things: either the temperatures of the object that EMITTED the wave (which can be calculated using Wien's displacement law, or more generally Planck's law) or it simply means that they multiplied the frequency by Planc's constant (=the energy if the photons) and then divided by Boltzmann's constant. $T=\hbar \omega/k_B$

The latter is actually quite common and is done for convenience when dealing with some systems, note that you can obviously also invert this relationship and measure "temperature" in units of Hz (something I use quite frequently) or measure potential energy in Kelvins.

 

[astrokreng]

Temperature is a measure of the average kinetic energy of the particles in a substance. In other words, it represents the average vibration or movement of the atoms or molecules in a substance. This movement is related to the thermal energy of the substance, which is a form of energy that is transferred from hotter objects to colder objects.

The relationship between temperature and electromagnetic (EM) waves is that the temperature of a substance can affect the behavior and properties of EM waves passing through it. This is because as the temperature of a substance increases, the kinetic energy of its particles also increases, leading to more vigorous vibrations and collisions between the particles. This in turn can affect the speed, wavelength, and frequency of EM waves passing through the substance.

When we say that the temperature of an EM wave is X Kelvin, it is not referring to the temperature of an individual wave, but rather the temperature of the substance through which the wave is passing. This is because the temperature of a substance can affect the properties of all EM waves passing through it, not just a specific individual wave.

Your understanding of temperature in relation to an aluminum rod and wood is generally correct. In the case of the aluminum rod, both the atoms and free electrons contribute to its temperature because both are in motion and have kinetic energy. In wood, only the atoms contribute to the temperature because wood does not have free electrons like metals do. However, it is worth noting that the temperature of a substance is not solely dependent on the movement of its particles, but also on other factors such as the substance's specific heat capacity and thermal conductivity.