Black-Body Radiation of a Star

A star approximates a perfect black body, emitting radiation described by Planck’s law. The simulation plots the spectral emissive power versus wavelength, highlighting the visible band in its natural colours and marking the ultraviolet and infrared regions. The peak wavelength follows Wien’s law, and the total emitted power follows the Stefan‑Boltzmann law.

Students can select a preset star (Betelgeuse, Sun, Sirius, Rigel, Spica) or drag the temperature slider from 2000 K to 30 000 K. As the temperature changes, they observe the star’s colour shift, the movement of the spectrum’s peak to shorter wavelengths, and the increase in overall power. The board displays the corresponding Wien and Stefan values.

Through this interactive view, learners connect temperature to colour, understand how the spectrum shape reflects physical laws, and see quantitative evidence of the T⁴ dependence of radiated energy and the λ_max T constant of Wien’s law.