y travel about one to thre

e inches in the air
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er. Another radiation is the beta particle, basically a very light electron that moves at less than the speed of light. These particles are more energetic than alpha particles, but can be stopped by a thin sheet of metal or heavy clothing. The third form of nuclear radiation is the gamma ray. This is a type of electromagnetic radiation like visible light, radio waves and X-rays. They travel at the speed of light. It takes at least an inch of lead or eight inches of concrete to stop them. Finally, neutrons are also emitted by some radioactive substances. Neutrons are very penetrating but are not as common in nature. Neutrons have the capability of striking t scientists use the RBTF in terrorist explosive attack scenarios to evaluate responses of aircraft to energetic materials that may be carried onboard in the cargo and passenger sections of a commercial aircraft. The results of these tests are used to engineer safer aircraft for passenger travel.