wat is the uv catastrophe the fact that the radiation energy released continues to increase infinitly breakin g the law of conservation of energy or the fact thatthe experimental results did not comply with the classical theory
o Identify Planck’s hypothesis that radiation emitted and absorbed by the walls of a black body cavity is quantised. (discrete as opposed to continuous)
All objects at a temperature above absolute zero emit ‘thermal’ radiation.
The properties of this radiation depend on the temperature and the material from which the object is made from.
At low temperatures, objects emit infrared radiation and at higher temperatures they emit visible light.
The radiation consists of a continuos distribution of wavelengths from infrared to visible and ultraviolet.
Classical physics determined that radiation originates from thermally accelerated charges. This distribution of accelerations accounts for the continuous spectrum of the radiation.
A black body absorbs all radiation incident on it and reflects none. A cavity in a solid block is a good approximation. A small hole allows radiation to escape for spectroscopic analysis. The properties of this radiation depend only on the temperature and not the material from which the block is made.
It was thought that the energy absorbed and emitted by a black body should be continuous, that is, could occur in any amount, and should increase as the wavelength became shorter. This was not supported by the experimental data as shown in the sketch. The amount of energy radiated reaches a maximum at a wavelength that depends on the temperature of the black body.
Rayleigh and Jeans, in attempt to explain the shape of the curves, derived an equation for black body radiation that suggested that at low wavelengths (high frequencies) the energy density approaches infinity. Historically, the grossly unrealistic prediction at high (ultraviolet) frequencies became known as the “ultraviolet catastrophe”.
Planck suggested that radiation was emitted or absorbed by a black body in discrete quanta (packets of energy) (now known as photons) rather than continuously, as suggested by classical physics. This daring hypothesis led to the successful explanation of the shape of the energy density curves for black body radiation. With time and the contributions of many physicists, Planck’s hypothesis led to the development of a whole new branch of Physics called Quantum Physics.
The size of each quantum of energy is characteristic of the frequency of light emitted.
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