Monday, September 22, 2008
very little radiation
The manual for this device cautions that any reading under 10% of the scale is unreliable and a smaller scale should be used. So we can't really trust that the reading is correct, but we probably can reasonably suspect that the granite is not giving off gamma radiation in significant excess of the background radiation from all other sources (cosmic rays, etc).
I further suspect that this scale is actually in milli-roentgens per hour, not roentgens per hour (little 'r' rather than big 'R'). Otherwise the number would look like about 1,000 times greater than it should be, whereas if it's mR, it's about right.
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