In Living Color
With summer here we’re all looking for ways to keep cool. When it comes to what kind of clothes to wear you can sometimes get mixed messages. I’ve seen news reports telling people to wear loose white clothes and then the next year the anchor is recommending black shirts to beat the heat. Which color actually works better at keeping you cool? White does and to understand why we must turn to science.
When sunlight is shining on an object, the energy of the sunlight is absorbed by the atoms in 2 different ways. Atoms in a solid object do not “sit still”. They vibrate back and forth within the structure of the molecules. Temperature measure the average kinetic energy of the atoms. As light energy is absorbed by the atoms, the average kinetic energy increases, so the temperature of the object increases.
The valence electrons in the atoms of an object can absorb a specific amount of energy from sunlight. The energy causes the electrons to become unstable. In chemistry, we say that the valance electrons are in their excited state. To become stable, the electrons emit a specific amount of energy, which we see as a specific color of light. When sunlight passes through a prism, a rainbow of colors appears. White light contains the visible spectrum of colors, which are Red, Orange, Yellow, Green, Blue, Indigo, and Violet.
A red shirt looks red because the electrons have absorbed specific amount of energy from sunlight, became unstable, then emitted a specific amount of energy, which we see a red light. That is why a red shirt looks red. The energy of the remaining colors of light is converted into kinetic energy of the atoms, so the temperature of the red shirt increases.
The valance electrons, in the atoms of the elements of which the white shirt is composed, absorb the energy the different colors of light in sunlight, become very excited, and emit the different colors of light in sunlight. So, we see white light coming from the white shirt!
A very small portion of light energy is absorbed by the atoms and converted to kinetic energy, which we feel as heat energy.
So the white shirt is cool in sunlight.
What about the black shirt?
The valance electrons, in the atoms of the many different elements of which the black shirt is composed, absorb none of the energy of all the different colors of light in sunlight. Since no light was absorbed, no light is emitted. So our eyes receive NO LIGHT from the valance electrons, in the atoms of the many different elements of which the black shirt is composed! ALL of energy of the sunlight is absorbed by the atoms and converted to kinetic energy. So, the temperature of the black shirt increases more than a red, yellow, orange, green, blue, indigo, or violet shirt.
So the black shirt is very warm in sunlight!
If you’re the type of person who stays in the A/C all summer this information will have little effect on your wardrobe but if you’re the type of person that spends time outdoors be it running errands or running on a trail this tip should be useful. There are of course other things to take into consideration such material type and style of clothing. For example fibers that wick moisture away from the skin will help keep you dry and polyester will trap heat and sweat on the skins surface no matter what color. Cotton is a summer go-to but it has the potential to become saturated and soggy after prolonged activity.
All things considered, if you’re getting dressed for the day and need to decided between a black t-shirt and a white t-shirt the white shirt is the cooler option.
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