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Light – The Nature of Light

Albert Einstein won the Nobel Prize in physics in 1921 for introducing the idea that light cab be thought of as composed of tiny particles of energy, or photons, rather than as one continnuous wave. This idea revolutionized the way scientist thought of light, energy, radiation, and how they interact.

There’s the light we can see- the visible spectrum the light we can’t – ultraviolet, infrared and so on. Also, light behaves in certain ways, and we can manipulate and use this behavior to our advantage.

For example, we can use it to make our clothes seem brighter and whiter by fooling our eyes and make use of how we perceive. By reflecting light, we can see objects in space; reflect it even more precisely, and we have the laser, which has been applied to everything from surgery to art to computer technology.

But the uses for light don’t stop there. It has been employed in scanners, from digital and bar code scanner’s to retinal and iris scanner’s. Light sensitive diodes are used in security and detection systems in our homes. Thermography helps us predict and prepare for the intensity of storms. Night vision goggles help us see clearly in the dark.

Light and vision go hand in hand. How we see is a trick the brain plays on the eyes or may be vice versa and as we age vision naturally declines. How ever, light can help improve function in the form of eyeglasses, contacts, and ever laser surgery.

A COLORFUL EXPLANATION

Absorption of Light

So why we exactly are we able to see blue skies, pink sunsets, green grass and all other colors? When light hits an object, some electromagnetic radiation is absorbed, and some is reflected Atoms can absorb only those waves whose energy content corresponds with possible energy states those atoms can have rays it discards; A blue jacket for example, is that color because the atoms of chemical dye in the cloth absorb almost every wavelength except blue. Strawberries appear red because they absorb blue and green wavelengths. leaves are green because the pigments involved in photosynthesis happen to be most receptive to red and blue light.

Every wondered why the sky is blue? All wavelengths of sunlight get scattered by molecules and dust in the air but not equally. Blue light with its  shorter wavelength scatters more than red or orange, which have longer wavelengths. When you look at the sky and not the sun, you see indirect, scattered light making the sky appear blue.

HOW WE PERCEIVE COLOR

The human eyes has about three million color perceiving cones, which come in three different types, each favoring one of three ranges of wavelengths; red, blue, or green. We perceive color when the different wavelengths are absorbed and reflected, and each element has a slightly different set of wavelengths it can absorb. The millions of colors the human eye is capable or perceiving are made up of varying combinations of red, green and blue. Things that appear largely transparent to our eyes, such as air and water, don’t have the right energy levels to absorb visible light of any color.

There are three types of color receptors in your eye: red, green and blue. But how do we see the amazing kaleidoscope of other colors that make up our world?
From the TED-Ed Lesson How we see color – Colm Kelleher
Animation by TED-Ed

Article Source : National Geographic

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