What do x-rays, Ray Romano, and the Tampa Bay Rays have in common?
In a post a while back, I made the point that color really doesn't exist except in our minds. In order to have color in our minds, we have to have light. Put simply, color is light.
A Rainbow is a common display of the visible portion of the
Visible light is a small part of a much larger body of energy referred to as the electromagnetic spectrum. This spectrum is comprised of wavelengths of energy with the longest being over one kilometer long, while the shortest wavelength is measured in billionths of a meter (or millionths of a millimeter!). At the long end of the spectrum are radio waves and radar. At the other end of the spectrum where the waves are very short we find cosmic rays, gamma rays, x-rays, Tampa Bay Rays and Ray Romano. Okay, forget those last two. But if it wasn't for a portion of the electromagnetic spectrum, we wouldn't be able to see that Florida baseball team, or watch Everybody Loves Raymond. In a very narrow sliver somewhere in the middle of all those rays is a band of wavelengths that excites the retina at the back of our eyes, otherwise known as visible light. And we associate the different wavelengths in this range with different colors.
In a small band between roughly 380 nanometers and 700 nanometers (nanometer = billionth of a meter) there stands a house where Roy lives. You will remember Roy from high school art class. Or maybe he was in your physics class. You know, he was always such a colorful character.... Remember he had that strange last name... Roy G. Biv? He had such a range of emotions... One day his face was red with embarrassment, another day he was green with envy, and other times he would seem kind of sad and blue.
Of course Roy G. Biv is how many of us learned the color wheel. Red, Orange, Yellow, Green, Blue, Indigo, and Violet are the colors you saw as you went around the color wheel. They are also the colors you can see in the electromagnetic spectrum.
Just outside the visible spectrum next to violet sits ultraviolet (from Latin which means "beyond violet") energy. Remember the cool posters you had in your bedroom when you were growing up? No, not the posters of Farrah Fawcett or Donny Osmond. I'm talking about the velvet poster of the unicorn jumping over the florescent rainbow. Or maybe it was an Elvis poster (Presley or Costello). The kind that glowed under your black light. The black light bulb produces high energy ultraviolet light. These bulbs are called black lights because you can't see that part of the spectrum. UV brighteners are often added to things like laundry detergents, whitening toothpaste, and paper. They are added to help make products look "whiter than white". The added UV brighteners in paper and even printing inks can make color management challenging at times.
Ultraviolet light is also used in security to help thwart counterfeiters. if you hold a black light up to your driver's license, or any credit card, you will see a glowing UV watermark that was otherwise invisible to you. You can also see a glowing strip running vertically through all US paper currency except a one dollar bill.
On the other end of the visible spectrum and also invisible to the unaided human eye is the infrared (from Latin "infra" for below) range. Some animals can see into both this range and ultraviolet, especially more nocturnal species. Infrared imaging is used in many areas including photography, weather forecasting (IR satellite imagery), astronomy and the military to name a few. Infrared is used in night vision devices to see in dark environments.
Did you know that you can see into the infrared range by using some things that may be around you right now? Try this at your next party. But be warned, this experiment carries a geek factor of 7.2, so expect some backlash in some social situations. Okay, get a remote control and a digital camera. Almost any remote control will work as long as it is not an RF, or radio frequency, remote. Most are not. The digital camera that is on your cell phone will probably work fine. Aim the remote control at the camera lens, and while looking at the LCD screen on the camera, press a button on the remote control. You should see the bright white-purple light at the end of the remote control that is usually invisible to you. The light-sensitive CCD or CMOS chip in the digital camera can see into this part of the electromagnetic spectrum. Cool huh? Okay, it's not that cool, but it illustrates the point.
Don't go into the light! The front of an IR remote control
as seen by a digital camera
So the next time you use your remote control to change the channel so you can watch an excellent show like NBC's "The Office", think about how you are putting all that infrared energy to very good use.