Why is a light colored T-shirt cooler to wear than a dark colored T-shirt?
Asked by: Cameron Wilson
By 'cooler' I assume you are referring to temperature, not
making a fashion statement.
Sunlight consists of a mixture of all visible wavelengths
of electromagnetic radiation (light). When all visible
wavelengths enter the eye simultaneously, the color
white is perceived. Black is the absence of any light.
Other colors are sensed when selected wavelengths are
present--longer wavelengths are perceived as red, shorter
ones as blue or violet.
An object's color in the sun depends on which wavelengths
it absorbs and, therefore, which are reflected away from
the object. A shirt that appears red absorbs the shorter
wavelengths and reflects longer ones. The reverse is
true for a blue shirt. So while a white, or lighter
colored, shirt REFLECTS most of the visible wavelengths
it is exposed to, a black or dark shirt ABSORBS more
wavelengths. Absorbed radiation is converted into heat,
making the darker shirt warmer to wear.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor
'A scientist is happy, not in resting on his attainments but in the steady acquisition of fresh knowledge.'