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What is light? - all light is not the same

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What is light

What is light?
Light is electromagnetic radiation of a wavelength that can be detected by the human eye, which sees each wavelength as a different colour. The visible part represents only a tiny part of the full spectrum.

A rainbow shows the broad colour spectrum of visible light of which scientists believe there to be up to 10 million hues discernable by the human eye.

How Can You Tell Light Sources Apart?
Spectral Power Distribution (SPD) charts offer us a visual representation of the very different make-ups of different light sources. They compare the amounts of each wavelength that are present in the light beam. The SPD is used to compare and contrast the quality of different light sources and their impact on visual acuity and the body clock.

Fact #1
The sun is in fact white. It only appears yellow because the atmosphere scatters the light waves

Fact #2
Something called the genetic photic sneeze reflex means one in three of us sneeze when we look at the sun

Fact #3
A Jiffy is the time it takes light to travel 1cm in a vacuum

Vision happens when light waves reflect off objects and into our eyes. It is the light which allows us to see the objects. Human eyesight has always offered us an advantage over other species - our sight is, for example, seven times sharper than that of a cat.

Light plays a major role in how we perceive colour. The source of the light being shed determines the colours that are made available for the eye to see. Changing the light source changes what you can see.

It is not all physics. There is also a psychology to perception which describes how our individual brains make sense of light, sight and any other stimuli in the moment. This relates to memory and the inferences we each make automatically. Colour blindness and optical illusions are two examples of this phenomenon.

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