What is the most intense wavelength and frequency in the spectrum of a black body? Planck's Law is

Dominick Blanchard

Dominick Blanchard

Answered question

2022-05-14

What is the most intense wavelength and frequency in the spectrum of a black body?
Planck's Law is commonly stated in two different ways:
u λ ( λ , T ) = 2 h c 2 λ 5 1 e h c λ k T 1
u ν ( ν , T ) = 2 h ν 3 c 2 1 e h ν k T 1
We can find the maximum of those functions by differentiating those equations with respect to λ and to ν, respectively. We get two ways to write Wien's Displacement Law:
λ peak T = 2.898 10 3 m K
ν peak T = 5.879 10 10 H z K 1
We see that λ peak c ν peak . So what frequency or wavelength is actually detected by an optical instrument most intensely when analyzing a black body? If they are λ peak and ν peak , how is λ peak c ν peak ?

Answer & Explanation

priffEmipsy4i37m

priffEmipsy4i37m

Beginner2022-05-15Added 17 answers

If you measure the frequency distribution the peak is at ν peak and if you measure the wavelength distribution the peak is at λ peak . They are two different distributions.
If your optical instrument measures something else, then you have to explain exactly what.
The two spectral densities are not related in the way you expect because d ν and d λ do not have the same relation that ν and λ do.

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