Heat Radiation: When Does it Vibrate & Absorb Photons?

In summary, heat radiation involves the transfer of energy from photons to molecules, causing them to vibrate faster and increase in temperature. This occurs through the photoelectric effect, where incoming photons with enough energy can eject electrons from orbit, and through other methods such as Compton effect and photo-nuclear reactions. However, lower frequency photons can also interact with molecules and increase temperature.
  • #1
Cheman
235
1
Heat radiation...

When you heat up an object by radiation (ie - hit it with infrared photons) it gets hotter. Therefore, its atoms/ molecules must be vibrating faster. However, I have also been told that when an electron absorbs a photon it moves to a new evergy level and then releases the photon again as it returns to its ground state. So, when do these two different phenominum occur? ie - what must the photon in the 1st scenario strike, etc
 
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  • #2
It depends on the frequency of the photons. Lower frequency photons interact with molecules (like microwave ovens). At higher frequencies (light, near infrared, ultraviolet, and higher) electrons get excited. Einstein's Nobel prize was for analyzing how this works - photoelectric effect.
 
  • #3
ya, it all depends on the energy of the incoming photons. As you know, E = hf, or E = hc/(wavelength). The actual function for photoelectric effect is hc/(wavelength) = Wo + Ek. Where Wo is the work function of the metal or object. This work function represents the amount of energy needed to eject an electron out of orbit. But if the energy of the photon is too small (<Wo) then the electron will not be ejected but it will only absorb some of the energy, oscilate, and increase temperature. This is what separates the two scenarios. Does that answer your question.
 
  • #4
There are generally 4 methods in which an incoming photon can be absorbed or lose energy: Photo-electric effect, Compton effect, Pair production [high energy incoming photon (E>1.022MeV for e- e+)] , Photo-nuclear [(gamma,n); (gamma,p); ...] reactions [high energy incoming photon (E>threshold energy for reaction with given isotope, MeV range)] . From the infrared part of your question, I would like to add that no matter if it's IR, visible, UV, your photon will normally be absorbed and 'heat up' the radiated body (except like gamma rays that risk passing your body unharmed due to large penetrative power). At normal temperatures, a body irradiates a spectrum in the IR range indeed (varries with Planck spectrum vs temperature), this is to cool down. So, with Compton-, and at a little more energy of your incoming photon, Photo-electric effect, you get secundary electrons, which can transfer energy to the atoms of your body by elastic scattering, causing your body to heat up.
 

1. What is heat radiation?

Heat radiation, also known as thermal radiation, is the transfer of heat energy through electromagnetic waves. It does not require a medium to travel and can occur in a vacuum.

2. How does heat radiation occur?

Heat radiation occurs when an object with a higher temperature emits electromagnetic waves, which are then absorbed by another object with a lower temperature. This transfer of energy causes the lower temperature object to increase in temperature.

3. When does heat radiation vibrate?

Heat radiation vibrates at the speed of light, which is approximately 299,792,458 meters per second. This vibration is caused by the movement of the electromagnetic waves.

4. What are photons in relation to heat radiation?

Photons are the particles that make up electromagnetic waves, including heat radiation. They have no mass and travel at the speed of light. When an object emits heat radiation, it is releasing photons.

5. Can heat radiation be absorbed?

Yes, heat radiation can be absorbed by objects with a lower temperature. This absorption of energy causes the object to increase in temperature. However, some objects, such as shiny metals, can reflect heat radiation instead of absorbing it.

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