Light Mixing!

Posted by: on Apr 14, 2013 | No Comments

Can you make the colour ‘yellow’ with only red, green, and blue as your colour palette? If you’re a scientist, it’s not a problem. But if you’re an artist, you’re in trouble already.

The key is that we would be mixing light, not paint.colours

If you’re thinking yellow should be a primary colour – it is a primary colour, but only in the artist’s world. Yellow paint is a primary colour for painters, but yellow light is actually made from red and green light. Confused? Good, because we’re going to spin colours, mix and un-mix colours, and play with the electromagnetic spectrum. Let’s get started.


Mixing Colours of Light

Find three torches. Cover each with coloured cellophane or paint the plastic lens cover with nail polish (red, green, and blue). Shine onto a white ceiling or wall, overlap the colours and make new colours. Leave the torches on, line them up on a table, turn off the lights, and dance -you will be making rainbow shadows on the wall! In addition, you can paint the lens of a fourth torch yellow.

What’s Happening?

More About Mixing Colours:

When you combine red and green light, you will get yellow light. Combine green and blue to get cyan (turquoise). Combine blue and red to get magenta (purple). Turn on the red and green lights, and the wall will appear yellow. Wave your hand in front of the lights and you will see cyan and magenta shadows. Turn on the green and blue lights, and the wall turns cyan with yellow and magenta shadows. Turning on the blue and red give a magenta wall with yellow and cyan shadows.

Mixing the three primary colours of light gives white light. If you took three light bulbs (red, green, and blue) and shined them on the ceiling, you’d see white. And if you could un-mix the white colours, you’d get the rainbow. That’s what prisms do.

Turn on all colours and you will get a white wall with cyan, yellow, and magenta shadows – rainbow shadows!

Thanks to and adapted from Aurora Lipper