Black Body Radiation: Low Intensity at High & Low Frequqs

In summary, blackbody radiation exhibits two regions of low intensity - one at high frequencies and one at low frequencies. The low intensity in the high frequency region is due to the higher energy required to emit radiation, while the low intensity in the low frequency region is because of the smaller number of modes in which radiation can be emitted. Thermal energy is the mean energy of random motion of particles and while the energy of individual particles is quantized, thermal energy itself does not necessarily have to be quantized. However, for a more accurate model of blackbody radiation, the quantization of molecular oscillators must be taken into account.
  • #1
slft
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0
In black body radiation, there are two regions of low intensity. One is at the high frequencies and one is at the low frequencies. I understand that there is lower probability to emit radiation at high frequencies because it requires higher energy than the average thermal energy provided. However, why is there also a low intensity in lower frequencies? Is it also the because of low probability of receiving the low energy? If so, does it mean that thermal energy is also discrete?
 
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  • #2
I'd say that the low probability of emitting in the low frequency region is because the smaller number of modes in which you can emit. You can find a good explanation in http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html" [Broken]
 
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  • #3
so is thermal energy discrete?
 
  • #4
My understanding is that thermal energy is the mean energy of the random motion of the particles in a system. So I would say that the energy of the individual particles is quantized, but that thermal energy, being the mean value, does not necessarily have to be quantized.

But I am actually not sure about this, so maybe someone have a better answer.
 
  • #5
Pete99 said:
My understanding is that thermal energy is the mean energy of the random motion of the particles in a system. So I would say that the energy of the individual particles is quantized, but that thermal energy, being the mean value, does not necessarily have to be quantized.

But I am actually not sure about this, so maybe someone have a better answer.

If you mean by thermal energy the total random kinetic molecular energy, than this number will be discrete because it is a sum of discrete numbers. But a typical object has so many billions upon billions of molecules that the total thermal energy of an object is going to look so close to continuous that for practical purposes you might as well treat it that way. If you mean by thermal energy the average random kinetic molecular energy, than averages of discrete number sets are not discrete.

To get the correct model of blackbody radiation (one that matches experiment), you have to assume the molecular oscillators are quantized.
 

1. What is black body radiation?

Black body radiation is the electromagnetic radiation emitted by a perfect black body, which is an object that absorbs all radiation that falls on it and reflects none. It is a fundamental concept in physics and is used to explain the emission of light and heat from objects.

2. Why is black body radiation of low intensity at high and low frequencies?

This is due to the shape of the black body radiation curve, known as the Planck distribution. At high frequencies, the curve drops off rapidly, resulting in low intensity. At low frequencies, the curve is flatter, resulting in a lower intensity compared to the peak intensity.

3. How does black body radiation relate to temperature?

The intensity and frequency of black body radiation are both dependent on the temperature of the object. As the temperature increases, the peak intensity of the radiation shifts to higher frequencies and the overall intensity increases.

4. What is the significance of black body radiation?

Black body radiation is important in understanding and predicting the behavior of light and heat in various systems. It has applications in fields such as astronomy, thermodynamics, and quantum mechanics.

5. Can black body radiation be observed in real life?

Yes, black body radiation can be observed in various phenomena, such as the glow of a heated object, the light emitted by stars, and even the cosmic microwave background radiation left over from the Big Bang. However, perfect black bodies do not exist in nature, so these observations are not exact representations of black body radiation.

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