Question: What do the following things have in common?
- Hearing an ad for “Armor Hot Dogs” played over the radio.
- Cooking some hot dogs in the microwave oven.
- Roasting hot dogs over a campfire.
- Seeing mustard stains on your shirt from that hot dog you ate.
- Tanning on the beach after going to the hot dog stand.
The answer: They are all the result of Electromagnetic Waves! (oh, were you distracted by the hot dog references?)
Radio waves, Microwaves, Infrared waves (what we feel as heat), Visible Light waves, Ultraviolet waves… plus the mysterious X-ray waves, and Gamma-ray waves. Each and every one is an electromagnetic wave. Though each can do very different things, the only difference between them is the wavelength.
So what is wavelength? Really it’s about as simple as it sounds; it’s the length of a wave. If you think of ocean waves there are high spots (peaks) and low spots (valleys). If you measure from peak to peak you would have the entire length of one wave.
Some example wavelengths:
- AM Radio Station ~ 300 meters
- FM Radio Station ~ 3 meters
- Microwave oven ~ 1 foot
- Radar ~ 5 centimeters
- Body heat ~ 10 micrometres (micrometre = 1 millionth of a meter)
- The colour blue ~ 0.5 micrometres
- Sunburn inducing Ultraviolet ~ 30 nanometres (nanometre = 1 billionth of a meter)
- Gamma rays at the far end of the spectrum go beyond 0.003 nanometres across.
In the same way that a mountain and the beach are made of the same thing, sometimes size does matter.
Now hold on just a minute, buster! I have a question. Waves don’t really exist as a physical thing. It’s just a method of movement. I understand a wave of moving water, but what is a wave of electromagnetism? I mean, what “stuff” is moving?
Well, all electromagnetic waves move at the speed of light. The fact is, they are light. Or more accurately, light is them. So to answer what is an electromagnetic wave, you have to answer what is light?
That’s such an interesting question that I’m going to save it for next time.
- Source: NASA explains Electromagnetic Waves to Kids (or anybody else who wants a basic understanding)