Black Body Colors Explained by Wien's Law

The phenomenon of black body radiation, which describes the light emitted by objects solely due to their temperature, is explained by specific physical laws. The color observed is directly related to the temperature of the black body.

Wien's Displacement Law Explained

Wien's Displacement Law is the fundamental principle that connects the temperature of a black body to the wavelength at which it emits the most intense radiation. This peak wavelength determines the perceived color.

• The law states that the peak emission wavelength ($\lambda_{max}$) is inversely proportional to the absolute temperature ($T$) of the black body. Mathematically, $\lambda_{max} \propto 1/T$.
• Therefore, hotter objects (like hotter stars) emit more blue light (shorter peak wavelength), while cooler objects (like cooler stars or the Sun, relatively) emit more red light (longer peak wavelength). This law accurately describes the spectral distribution of thermal radiation.

Why Other Laws Are Incorrect

The other options provided relate to different areas of physics:

• Kepler's laws of planetary motion: Describe the orbits of planets around the Sun.
• Snell's Law: Governs the bending (refraction) of light as it passes between different media.
• Hooke's Law: Relates the force needed to extend or compress a spring by some amount to that same amount of extension or compression (describes elasticity).

None of these laws explain the relationship between temperature and the color (emission spectrum) of black bodies like stars.

Conclusion

Based on its function, Wien's Displacement Law correctly explains the colors of black bodies, including celestial objects like the Sun and stars, as a consequence of their temperatures.