As temperature increases, the peak emission wavelength of a blackbody shifts toward shorter wavelengths. What law describes this behavior?

As temperature increases, the peak emission wavelength of a blackbody shifts toward shorter wavelengths. What law describes this behavior?

• A. Stefan-Boltzmann law
• B. Planck's law
• C. Kirchhoff's law
• D. Wien's law

Answer: (D)

Shifts in the color of a hot object come from where its emission is strongest in the spectrum. Wien's displacement law states that the wavelength at which a blackbody emits most intensely is inversely proportional to its temperature: λ_max = b / T, with b ≈ 2.9 × 10^-3 m·K. So as temperature rises, λ_max gets smaller, and the peak moves to shorter wavelengths, which is why a hotter bulb glows more blue-white while a cooler object glows red. Planck's law describes the entire spectrum at a given temperature and is the basis for deriving Wien's law, while the Stefan-Boltzmann law tells you the total power emitted (P ∝ T^4) rather than where the peak lies. Kirchhoff's law relates emissivity and absorptivity but doesn't describe the peak shift with temperature.

Shifts in the color of a hot object come from where its emission is strongest in the spectrum. Wien's displacement law states that the wavelength at which a blackbody emits most intensely is inversely proportional to its temperature: λ_max = b / T, with b ≈ 2.9 × 10^-3 m·K. So as temperature rises, λ_max gets smaller, and the peak moves to shorter wavelengths, which is why a hotter bulb glows more blue-white while a cooler object glows red. Planck's law describes the entire spectrum at a given temperature and is the basis for deriving Wien's law, while the Stefan-Boltzmann law tells you the total power emitted (P ∝ T^4) rather than where the peak lies. Kirchhoff's law relates emissivity and absorptivity but doesn't describe the peak shift with temperature.