Does the amount of radiation (cpm) increase or decease as the distance between the source and the sensor increases?

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ncchemist | eNotes Employee

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We are asked if the amount of radiation increases or decreases with respect to distance between the source and sensor.  The answer is that it decreases.  The further away you move from a source of radiation, the weaker the radiation measured becomes.  That is because radiation follows the inverse square law with regards to distance.  That is to say that the intensity of the radiation varies inversely with the square of the distance from the source.  So as you move further away, the intensity does not merely drop off at a linear level but at an exponential level.

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