Electromagnetic waves are transverse waves, which means that they oscillate perpendicular to the direction of motion. If the wave moves left to right, it will oscillate up and down. Electromagnetic waves are basically ‘light waves’ but not all of them are visible. The electromagnetic spectrum ranges in wavelengths from thousands of meters to a trillionth of a meter long. The only kind of electromagnetic wave we can see with our bare eyes is visible light, which is only a tiny fraction of all electromagnetic waves. The visible spectrum only ranges from 700-400 nanometers (billionths of a meter).

Electromagnetic Spectrum Waves

1. Radio Waves - Lowest-energy electromagnetic waves. Longest electromagnetic waves (longer than 0.3 meters). Transmit the music you hear on the radio.
2. Microwaves - Between 0.3 meters and 0.003 meters. These waves cook the food in your microwave by vibrating the water molecules in your food.
3. Infrared Waves: A tiny bit longer than red light in the visible spectrum. Warm objects give off infrared waves, so you can think of infrared as ‘heat’.
4. Visible Light - Light that humans can see is in this spectrum. The colors of visible light, from longest wavelength to shortest, are red, orange, yellow, green, blue, indigo, violet. Think of a person named ROY G BIV to help you remember.
5. Ultraviolet Rays - Smaller frequency and higher energy than visible light. The sun emits UV rays that cause the sunburn you get at the beach.
6. X-Rays - Higher energy and higher frequency than UV rays. X-rays can pass through skin and flesh but not through bone, so they are used to examine bones.
7. Gamma Rays - Highest-energy and highest-frequency waves. These radioactive rays are harmful to humans and other living things.

You can remember the order of the electromagnetic spectrum from highest to lowest energy if you memorize this sentence: Raging Martians Invaded Venus Using X-ray Guns. (Look at the first letter of each word.)

The Speed of Light - Electromagnetic waves travel incredibly fast. They travel almost 300,000 kilometers per second. It takes about 8.5 minutes for light to travel about 150 million kilometers from the sun to Earth. Light waves reflect off of objects and enter our eyes. Usually, we think of light as white, but actually white light is every color combined. When light is refracted, the colors of white light separate out into each distinct wavelength of light.