Which cools faster black or white

If it is absorbed, the substance looks black. If it isn't, it's white [because the light is reflected back]. This means that, if you heat something up, if there's [a higher energy level] somewhere for the electrons to go up to, and it's black, then there's also somewhere for the electron to drop down to again, meaning that the substance will also emit energy.

So if something is good at absorbing light then it's also good at emitting it. So a black thing should be much better at emitting light than a white thing. Chris - So if you have solar panels on your roof, for example, that are heating water, you don't want the water going through them when it's colder outside than the water is because you're turning them into very effective giant radiators?

Dave - That's right. And if you want to cool down a spaceship, the only way of doing it is by radiation of infrared light, so you paint the outside of your spaceship, or the bits of the radiators, in really dark black, which is so much better at emitting the light a much better radiator.

Chris - Alright; slight twist to the story: if you're a cricketer and your at Lords, assuming it is sunny on the occasion you're over there - not that we've been having much sun lately - they wear white, ostensibly to reflect the heat back off.

So would they be better off wearing black then, assuming they're going to get hot anyway, so they can radiate the light and the heat better with the black surface? Dave - They're very, very unlikely to be hot enough to be radiating more heat than the sun is putting down on them because the sun has got a kilowatt per square metre and you're going to have to be very, very warm before you're emitting that much heat. So, I think you're still better off being in white. Skip to main content.

Earth Science. Articles Answers to Science Questions What loses heat fastest, a white or black surface? What loses heat fastest, a white or black surface? Does a black object emit thermal radiation more readily than a white object? Part of the show Why do some animals dump indiscriminately?

Play Download. Or, if the sun is your light source, just hold the card in the sunlight. Note: this Snack does not work with LED or fluorescent lights. In sunlight, it works best when it's bright out but not too hot or too cold.

Watch the liquid crystal side of the card. Notice that the side with black on the back changes color faster than the side with silver on the back. This color change indicates that the blackened side is changing temperature faster than the silvered side.

Let the card cool until the liquid crystal is black again. Then heat up the card by touching it to your hand or forehead, or by shining light onto the liquid crystal side. Remove the card from the heat and watch the liquid crystal as it cools. The black side should cool faster than the silver side. Dark-colored materials absorb visible light better than light-colored materials. The lighter side absorbs less of the incident light, reflecting some of the energy.

Darker materials also emit radiation more readily than light-colored materials, so they cool faster. You may be tempted to skip coating half of the card with the silver marker.

After all, that half is probably white, which indicates that it reflects light in the visible portion of the electromagnetic spectrum. But, although the white paper reflects visible light, it also absorbs infrared light. If you could see infrared light, the white paper would look black when illuminated with infrared.

Unlike plain white paper, silver paint reflects infrared light as well as visible light. Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. Recently, I found an exercise in which a graph was shown with the variation of temperature of two painted cans as they received sunlight.

One of the questions was "Which of these two bodies will cool down faster? I thought it was the white can and for my surprise i found out I was wrong. Can someone explain me why? Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.