Lecture: Wavelength of peak intensity

Contemporary Challenges 2021
This very short lecture introduces Wein's displacement law.

This lecture is needed if Wein's law homework is used.
We saw previously that the spectral intensity can be expressed with respect to wavelength: \begin{align} S_{\lambda}(\lambda) &= \frac{2\pi h c^2}{\lambda^5}\frac1{e^{\frac{hc}{\lambda k_BT}}-1} \end{align} I mentioned that the peak intensity shifts to lower wavelengths at higher temperature. We can solve for the peak in the spectral intensity by taking a derivative. The resultin equation can

but the result is a non-linear equation that is a bit of a pain. So it's convenient to just have an equation. The result is known as Wien's displacement law, and states that \begin{align} \lambda_{\text{peak}} &= \frac{b}{T} \end{align} where \(b=2.9\times 10^{-3}\text{ m K}\) is called Wien's displacement constant.

Wein's displacement law blackbody radiation
Learning Outcomes