Question answered by Marilyn Case, Health Physicist, GSS ESER Program www.gsseser.com
Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic (EM) radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves, infrared light, ultraviolet light, X-rays, and gamma-rays. The electromagnetic spectrum is the term used by scientists to describe the entire range of light that exists. Only a small sliver of the light that surrounds us is visible – most of the light in the universe is, in fact, invisible to us!
Electromagnetic radiation can be described in terms of a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light. It is defined by energy; frequency, which counts the number of waves that pass by a point in one second; and by wavelength, which is the distance from the peak of one wave to the peak of the next.
Your radio captures longer wavelength radio waves emitted by radio stations, bringing your favorite tunes. Radio waves are also emitted by stars and gases in space. Gamma rays have the smallest wavelengths and the most energy of any wave in the EM spectrum. They are produced by the hottest and most energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around black holes. On Earth, gamma waves are generated by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.
Gamma rays and X-rays can ionize or remove electrons from an atom. Ionizing radiation absorbed by human tissue has enough energy to remove electrons from the atoms that make up molecules of the tissue and may thus cause cell damage.
Microwave ovens heat food like the sun heats your face—by radiation.
Microwave ovens use microwaves waves, which are part of the electromagnetic spectrum. The oven sends the waves back and forth through your food. This causes the water, fat, and sugar molecules in the food to rotate and bump into each other, which produces heat. This heat is what actually cooks food in the oven.
The microwaves that cook food in your oven are roughly 5 inches long. Despite their small size, microwaves carry a huge amount of energy.
Materials: A bar of Ivory soap (don’t try this with any other brand of soap), paper plate, microwave oven
- Place the Ivory soap on the plate.
- Put the soap in the oven and set the timer for 2 minutes on the high setting.
- Pull up a chair and watch what happens! The soap will start to rapidly expand after about 15 seconds.
- When your microwave stops, let the soap cool for a minute.
- Remove the soap from the oven and examine it.
Ivory soap contains small pockets of air that have water vapor trapped inside of them. The water vaporizes, forming bubbles, and the heat causes trapped air to expand. This is actually very similar to what happens when popcorn pops.
Microwaved Ivory soap on left; fresh Ivory soap bar on right for size comparison. Note: Although heating up soap in the microwave will not damage your microwave or the food you heat in it later, it will cause the microwave to smell like soap for a few hours.