Physics
Physics
Problem
(i) State Wien’s displacement law for blackbody radiation, clearly identifying each physical quantity involved. (ii) Using this law, explain qualitatively how the predominant colour of radiation emitted by a blackbody changes as its temperature is raised from about to . Quote the approximate visible wavelength bands for red, yellow and blue light in your discussion. (iii) An electric room-heater element is seen to glow dull red soon after it is switched on, but after a few minutes appears almost white. Give a reasoned explanation for this observation on the basis of part (ii).Intuitive explanation
Wien's displacement law connects the temperature of a glowing object to the wavelength at which it radiates most intensely—hotter objects emit their peak radiation at shorter wavelengths. As temperature rises, the peak shifts from infrared through red, yellow, and into blue, which is why hot objects change colour from dull red to white. This law is the key to understanding why all hot objects follow the same colour sequence regardless of material.
Intuitive explanation
Wien's displacement law connects the temperature of a glowing object to the wavelength at which it radiates most intensely—hotter objects emit their peak radiation at shorter wavelengths. As temperature rises, the peak shifts from infrared through red, yellow, and into blue, which is why hot objects change colour from dull red to white. This law is the key to understanding why all hot objects follow the same colour sequence regardless of material.