Light comes in a range of wavelengths from smaller than billionths of a meter to larger than billions of meters long. Our eyes detect a very, very small fraction of that electromagnetic radiation in the nanometer (billionth of a meter) range. From red to violet, the wavelength ranges from about 800 nanometers to 400 nanometers. The light from the Sun contains a wide range of wavelengths, including ultraviolet light (UV) (which is smaller wavelength than visibile light), all the colors of the rainbow, and lots of infrared (IR) radiation.
Our eyes don’t detect the UV or IR light – we see the mixture of all the different colors of light together, which makes white. Artificial light (like fluorescent) generates a different mixture of wavelengths, which is why it looks different than sunlight.
You see the colors of objects because all materials absorb some wavelengths (colors) of light and reflect others. When light hits a red object, as I’ve shown at left, all colors except red are absorbed and what comes to your eyes is just the red light.
White surfaces reflect a wide spectrum of wavelengths and absorb very little of the spectrum. The light that is incident on a white surface is reflected back to our eyes and the broad spectrum of wavelengths we see as ‘white’. Black is the opposite: black absorbs a lot of different wavelengths, so very little reflects back to our eyes and we get black.
In addition to the visible light, the spectrum from the sun includes the aforementioned ultraviolet and infrared waves. Infrared radiation has longer wavelengths than red light. We don’t see it – we sense it as heat. You’ll notice that the lamps they use to keep food warm always have a red glow: they output some visible light, but they mostly output heat . You will never see food being kept warm by blue light.
Our eyes don’t detect the UV or IR light – we see the mixture of all the different colors of light together, which makes white. Artificial light (like fluorescent) generates a different mixture of wavelengths, which is why it looks different than sunlight.
You see the colors of objects because all materials absorb some wavelengths (colors) of light and reflect others. When light hits a red object, as I’ve shown at left, all colors except red are absorbed and what comes to your eyes is just the red light.
White surfaces reflect a wide spectrum of wavelengths and absorb very little of the spectrum. The light that is incident on a white surface is reflected back to our eyes and the broad spectrum of wavelengths we see as ‘white’. Black is the opposite: black absorbs a lot of different wavelengths, so very little reflects back to our eyes and we get black.
In addition to the visible light, the spectrum from the sun includes the aforementioned ultraviolet and infrared waves. Infrared radiation has longer wavelengths than red light. We don’t see it – we sense it as heat. You’ll notice that the lamps they use to keep food warm always have a red glow: they output some visible light, but they mostly output heat . You will never see food being kept warm by blue light.
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