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.	HPS and CRCPD Proclaim 8-14 November 2009 as National Radiation Protection Professionals Week
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.	2010 HPS Midyear Topical Meeting Radiation Risk Communication to the Public 24-27 January 2010 Albuquerque, NM
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07 November 2009

Answer to Question #598 Submitted to "Ask the Experts"

Category: Radiation Basics — Photons

The following question was answered by an expert in the appropriate field:

Which type of radiation has shorter wavelengths and is more radioactive—gamma rays or x rays?

Gamma rays are emitted by a variety of radioactive materials, some of the better known being ⁶⁰Co and ¹³⁷Cs. X rays, in contrast, are produced by radiation-producing machines, the most common being the x-ray machines used in medicine and dentistry. Neither gamma rays nor x rays are radioactive. They are pulses of energy that move through space at the speed of light. Once released, there is no way to tell the difference in these two types of rays or their origin. During the early years, the x rays produced by x-ray machines were of lower energy than those of typical gamma rays. As machines capable of producing higher energy x rays were developed, and as scientists gained a deeper understanding of the full range of energies of the gamma rays emitted by radioactive materials, they realized that the energies of the two types of rays overlapped. In general, however, gamma rays have higher energies than x rays. Since the shorter the wavelength, the higher the energy, it is also true that, in general, gamma rays have shorter wavelengths than x rays.

Dade W. Moeller, CHP

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