Question Video: Describing the Quantity Measured in the Unit Science

Which of the following is measured by the unit rem? [A] The radioactivity of an object. [B] The nuclear radiation absorbed by a person. [C] The intensity of nuclear radiation at a point.

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Video Transcript

Which of the following is measured by the unit rem? (A) The radioactivity of an object, (B) the nuclear radiation absorbed by a person, (C) the intensity of nuclear radiation at a point.

Let’s think about these three answer options in the context of a person being exposed to nuclear radiation. For a person to be exposed to radiation, first, there needs to be some object, say, this one here, that emits radiation. So let’s say this object is indeed giving off nuclear radiation and that a person is exposed to it. While some of this radiation may pass right through the person, some may also be absorbed. When this happens, there is a transfer of energy to the atoms in the person’s body that absorbed the radiation.

The unit rem is designed to indicate just how large of a dose of radiation is absorbed. If the unit rem described the radio activity of an object, then in our sketch we wouldn’t need to involve a person. We would just consider this part of the diagram. But this unit does have to do with how a person experiences, that is, absorbs, radiation. We won’t choose answer option (A).

Considering option (C), this claims that the unit rem has to do with the intensity of nuclear radiation at a point. Once again, this definition has nothing to do with how much radiation a person absorbs. If option (C) was correct, we could pick a point in space, say, this point here, and use the unit rem to indicate the intensity of nuclear radiation at that point. However, the unit rem is used for medical purposes. It’s designed to help safeguard people from being overexposed to nuclear radiation.

The unit rem gives a quantitative measure of the amount of nuclear radiation absorbed by a person. Notice that this does not include any nuclear radiation that the person will be exposed to but that they don’t absorb. This points to the fact that the unit rem is designed to support human health and safety.

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