You know the air in the atmosphere mainly looks clear and colorless, so you may be wondering why the sky looks blue. Sunlight appears one color, but what you perceive as white light is really a mixture of colors. You can use a prism to separate light into its spectrum the rainbow to see this for yourself. When light enters the atmosphere the colors react differently to gas molecules and small particles in the air.
Even though the atmosphere looks clear, it contains tiny particles of dust, ash, and water droplets. Shorter wavelengths of light, like violet and blue, are scattered by these particles. As a result, blue is scattered more than any other color, which is why the sky appears blue most of the time.
As the sun goes down, its light has to travel through more of the atmosphere before it reaches the planet. This means that by the time you see it, more of the blue light is already scattered, leaving the red and yellow light visible.
This is why sunrises and sunsets are red. The answer, according to researchers at the University of California, Riverside, is that the physiology of the human eye makes us more sensitive to blue light than to purple light. By Brooke Kuei Dec 3, The sun emits white light that holds the wavelength of all colors.
Like bananas, atoms , molecules and particles in the atmosphere absorb and scatter light. If they didn't, or if the Earth had no atmosphere, we would perceive the sun as a very bright star among others in a sky of perpetual night.
Not all wavelengths in the visible light spectrum scatter equally, however. Shorter, more energetic wavelengths, toward the violet end of the spectrum, scatter better than those toward the longer, less energetic, red end. This tendency is due in part to their higher energy, which allows them to ping-pong around more, and in part to the geometry of the particles that they interact with in the atmosphere.
In , Lord Rayleigh derived a formula describing a subset of these interactions, in which atmospheric particles are much smaller than the wavelengths of the radiation striking them. The Rayleigh scattering model showed that, in such systems, the intensity of scattered light varies inversely with the fourth power of its wavelength.
In other words, shorter wavelengths -- like blue and violet -- scatter a lot more than long ones when particles -- such as oxygen and nitrogen molecules -- are relatively small. Under these conditions, scattered light also tends to disperse equally in all directions, which is why the sky appears so saturated with color [source: Bohren ]. If we were foolish enough to look directly at the sun, we would see all wavelengths, because light would be reaching our eyes directly. That's why the sun and the area around it look white.
When we look away from the sun, at the clear sky, we see light mostly from shorter, scattered wavelengths like violet, indigo and blue. So why doesn't the sky appear violet instead of light blue? The eyes have it. Keep up. Subscribe to our daily newsletter to keep in touch with the subjects shaping our future. Topics About Us Contact Us. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Futurism.
Fonts by Typekit and Monotype.
0コメント