why the electromagnetic theory can't explain black body radiation.explain?

Asked by Akshay Hemke | 20th Jul, 2013, 12:07: PM

Expert Answer:

a. The blackbody spectrum depends only on the temperature of the object, and not on quality of material. An iron nail, a ceramic pot and a piece of coal would  emit the same blackbody spectrum at same temperatures . 

b. As the temperature of an object increases, it emits more blackbody energy at all wavelengths.

c. As the temperature of an object increases, the peak wavelength of the blackbody spectrum becomes shorter (bluer). For example, blue stars are hotter than red stars. 

d. The blackbody spectrum always becomes small at the left-hand side (the short wavelength, high frequency side).

 

Light is produced as an electromagnetic wave that is produced when an electric charge vibrates. Now , heat is just the kinetic energy of random motion. In a hot object, electrons vibrate in random directions and produce light as a result. A hotter object means more energetic vibrations and so more light is emitted by a hotter object --- it glows brighter. But the shape of the blackbody spectrum could not be explained.

 

The electrons in a hot object can vibrate with a range of frequencies, ranging from very few vibrations per second to a huge number of vibrations per second, each frequency of vibration should have the same energy. Since there is no limit to how great the frequency can be, there is no limit to the energy of the vibrating electrons at high frequencies. This means that, there should be no limit to the energy of the light produced by the electrons vibrating at high frequencies.

 But, Experimentally, the blackbody spectrum always becomes small at the left-hand side (short wavelength, high frequency).

 

Thus we say that the theory does not explain Black Body radiations.

Answered by  | 21st Jul, 2013, 10:32: AM

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