WHAT IS COLOUR?

LUMINOSITY

I was looking at a painting a few days ago and its LUMINOSITY struck me.

It seemed to shine with a particular quality although the effect is by clever use of certain tints of paint …. and as someone who also paints I was curious as to what gave it that brightness. The English Romanticist, landscape painter,  JMC Turner, was recognised for his ability to use reflective light which gave his work this luminescent quality.

Luminous means to emit light .. but to be described as such that light must not have been created by heat!  So paintings, photographs, objects that appear luminous emit more light than their surroundings. And the createst souce of luminosity in our solar system is our SUN 

Luminous is quite a vague word really. Arguably, even a flashlight bulb is luminous, because it turns electricity (electrical energy) into light and shines it toward us. But bulbs like this are incandescent and make light by making heat. They illuminate things but they are not luminous. Luminescent things, by contrast, make light when their atoms become excited in a process that needs little or no heat to make it happen.

What other types of luminescence are there?

Of course there are many other sorts of luminosity … some I had never even heard of:
For example if you shine a light on a luminous watch and it shines straight back at you! That’s an example of what we call photoluminescence luminescence made by light.

But you can make things give off light by exciting their atoms with many other kinds of energy.  I am sure you have heard, if of not seen, the result of a chemical reaction that takes place in some animals such as fireflies, glow worms and many marine creatures living at depth

  • Bioluminescence: made by living creatures such as fireflies, glow-worms, and many marine creatures.
  • Chemoluminescence: made by a chemical reaction. Glow sticks work this way.
  • Electroluminescence: made by passing electricity through something like a gas.
  • Photoluminescence: made by shining light at “luminous” (phosphorescent) paints.
  • Sonoluminescence: made by passing energetic sound waves through liquids.
  • Thermoluminescence: made when photons are emitted from hot materials.
  • Triboluminescence: made by rubbing, scratching, or physically deforming crystals.
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