Friday, January 18, 2008

Visible Light Spectrun

I was over visiting a friend this afternoon. They have a prism suspended near the window so that the afternoon sunlight casts a light spectrum on the wall.

It was just beautiful. And it reminded me that this is only the part of the light spectrum that the human eye can see.

Beyond the red is infrared light. Which our skin can feel as warmth. Some snakes see very well indeed in this color range. Lots of other animals can see some of these colors which are well beyond the range that our eyes can detect. Just like dogs, bats, and dolphins can hear sounds higher in frequency than we can, and elephants can hear sounds lower in frequency than the human ear is capable of.

On the short wavelength portion of the spectrum, beyond the blue and purple, is what we normally refer to as ultraviolet (or black light). In water purification or medical environments these wavelengths (or colors) of light can used to can kill germs. In the upscale spas or tanning salons these invisible rays of light can tan our skin, help make vitamin D, and in heavy doses cause aging of the skin and then skin cancer.

These same ultraviolet light waves that our eye cannot see also make fluorescent minerals light up delightfully.