Black Body Radiation Flashcards
What is a black body?
A black body is an ideal system which absorbs any radiation that is incident on it.
What are two examples of black body?
- The sun.
- A piece of charcoal.
(They do not reflect any absorbed light that is incident on it)
What is Steffan’s law?
It states that the total heat power (P) radiated by a body is directly proportional to the fourth power of its temperature (T⁴)
What is a black body radiation?
Black body radiation is the radiation an ideal black body would emit when luminous.
What does Maxwell’s electromagnetic theory roughly mean?
Maxwell’s theory suggests that oscillating charged particles produce electromagnetic waves and the radiation emitted by a material might be due to the oscillation of charged particles in it.
What couldn’t Maxwell’s theory predict?
Maxwell’s theory couldn’t predict the observed spectrum of emitted light.
How do Weins and Rayleigh-Jeans attempt to predict this?
They propose a curve (based on classical theory) to explain and predict the spectrum of emitted light.
What was Weins and Rayleigh-Jeans’ error?
Their proposed curve (Classical Theory) agreed with observed for longer wavelengths but as wavelength tended to zero (UV region) they claimed the intensity of the radiation would rise to infinity instead of approaching zero as well.
What is Ultraviolet catastrophe?
This is the disagreement between the curve proposed by Weins and Rayleigh-Jeans, and the experimental data for shorter wavelengths (UV region) of spectrum of emitted light from black bodies.
How did Planck solve the ultraviolet catastrophe?
Planck proposed that instead of energy of any molecular vibration occuring as a continuous value, it existed as whole number multiples of the minimum energy (E = hf)
Thus, E = nhf.
