Compared to objects at cooler temperatures, what EMR wavelengths are emitted from objects at higher temperatures?

• A. Longer
• B. Similar
• C. Variable
• D. Shorter

Answer: (D)

Wien’s displacement law shows that as temperature rises, the peak of an object’s thermal radiation shifts to shorter wavelengths. Hotter objects emit photons with higher energy, so the most intense part of their spectrum moves from infrared toward visible and even ultraviolet. A familiar cue is metal cooling from red-hot to white or blue as it gets hotter. So, when comparing objects, those at higher temperatures emit shorter wavelengths overall, even though their total power increases with temperature as described by the T^4 relationship.