CAIE A-Level Physics 25.2.1 Wien's Displacement Law

Practise applying Wien’s displacement law to calculate a star’s peak emission wavelength or surface temperature and interpret spectrum changes.

Exam points

use Wien’s displacement law to calculate a star’s peak wavelength or surface temperature
interpret a star’s emission spectrum when its peak wavelength or temperature changes

[Maximum number: 2]

The wavelength $\lambda_{\text {max }}$ of light for which the maximum rate of emission occurs from the Sun is $5.00 \times 10^{-7} \mathrm{~m}$ .
The temperature of the surface of the star Sirius is 9940 K .
Use information from (d) to determine the wavelength of light for which the maximum rate of emission occurs from Sirius.
wavelength =
m

$\begin{aligned} \lambda_{(\max )} \propto \frac{1}{\mathrm{~T}} \frac{5.00 \times 10^{-7}}{\lambda}=\frac{9940}{5770} \end{aligned}$

C1

$\lambda=2.90 \times 10^{-7} \mathrm{~m}$

A1

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25.2.1—Wien’s displacement law λmax ∝ 1 / T to estimate the peak surface question 1