Maps and Charts
pick your dose
Scientists use three different ways of measuring the energy in radiation. Here they are:

CURIE Unit of Activity (A) A= # of decays
per second
1 curie = 3.7 × 1010
Decays per second

RAD Unit of Absorbed
Dose (D)
D = the energy
absorbed per gram
of tissue in the
1 rad = 100 ergs per gram

REM Unit of Dose
Equivalent (H)
H = the absorbed
dose multiplied
by a biological
factor (Q)
1 rem = Q × D

The best tool to measure an individual's risk from radiation exposure is the REM. In this formula, Q is really a weighting factor that represents the density of the ionization from various radiation types: alpha, beta, gamma particles, protons, neutrons that are emitted by a substance. Low level exposures are measured in millirems, or MREM, a thousandth of a rem.

One chest X-Ray gives you about 10 mrem of radiation, or .01 rem.
A dental X-Ray emits 1 mrem, or .001 rem.

home | did you know? | maps & charts | interviews | readings | glossary | reactions | faqs | join in
web site copyright 1995-2014 WGBH educational foundation
PBS Online