PHYSICS · Single correct · A Level · Physics · Particles and radiation · AP
Problem
A metal rod is slowly heated from 800K to 3000K. Which statement best explains why its visible color changes from dull red to nearly white as the temperature increases?
(a) Higher temperature increases the intensity at all wavelengths equally, so the rod merely looks white because it is brighter.
(b) Heating the rod shifts the peak wavelength toward longer values, adding more orange and yellow light that blend with red to appear white.
(c) Raising the temperature shifts the peak wavelength toward shorter values, so proportionally more blue and green light is emitted.
(d) At very high temperatures the metal’s atoms emit many discrete spectral lines across the visible range, and their combination produces white light.