Middle School Physical Science: Electromagnetic Radiation - The Electromagnetic Spectrum — Flashcards

The entire electromagnetic spectrum, from the lowest to the highest frequency (longest to shortest wavelength), includes all radio waves (e.g., commercial radio and television, microwaves, radar), infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

X Rays and Gamma Rays    
The shortest-wavelength, highest-frequency electromagnetic waves are X rays and gamma rays. These waves have so much energy that they can pass through many materials. This makes them potentially very harmful, but it also makes them useful for certain purposes.    
X rays have enough energy to pass through soft tissues such as skin but not enough to pass through bones and teeth, which are very dense. The bright areas on an X ray film show where X rays were absorbed by the bones or teeth.    
X rays are used not only for dental and medical purposes but also to screen luggage at airports. Too much X ray exposure may cause cancer. If you've had dental X rays, you may have noticed that a heavy apron was placed over your body to protect it from stray X rays. The apron is made of lead, which X rays cannot pass through.    
Gamma rays are the most energetic of all electromagnetic waves. They can pass through most materials, including bones and teeth. Nonetheless, even these waves are useful. For example, they can be used to treat cancer. A medical device sends gamma rays to the site of the cancer, and the rays destroy the cancerous cells.