an idealised object which absorbs and emits all frequencies of the electromagnetic spectrum.
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What is the radiation intensity against wavelength graph dependent on?
Temperature of the black-body (it is not dependent on the material of the black-body)
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State the Stefan -Boltzmann law
P/A = sigma*T^4 (where P: total thermal energy; A:area;T: temp)
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State the Wien's law and when it is suitable
I(lambda,T) =( 2hc^2/lambda^5) *e^-(hc/lambda*k*T) --> this only works for short wavelengths ; where I(lambda,T): amount of energy per unit surface area per unit time
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State Wien's displacement law
lambda_max *T= C (where C:2.898*10^-3 mK; for body temperature of 310K lambda_max = 9*10^-6)
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State Rayleigh -Jeans law and when it fails
I(lambda,T) = 2pi*cK_b *T/lambda^4 --> this equation does not work for short lambda's , this failure is called the ultraviolet catastrophe
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What did Planck propose?
Planck proposed that a blackbody contains oscillators which are constrained by a certain value of E_n. This is where planck's equation stem's from; E_n=nhf;delta E= hf where n,the quantum number is 1 and h is planck's constant 6.63*10^-31Js.
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What are the implications of Planck's equation
Emission and absorption of electromagnetic wavelengths happen due to the transitions to different energy levels (energy is dependent on frequency)
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State Planck's equation for the wavelength distribution of a Blackbody
I(lambda,T)= (2pi*h*c^2)/lambda^5(e^(hc/lambdaK_B*T)-1) ] this equation works for all wavelengths
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Other cards in this set
Card 2
Front
What is the radiation intensity against wavelength graph dependent on?
Back
Temperature of the black-body (it is not dependent on the material of the black-body)
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