What is the difference between sievert, roentgen, and gray? Why is radiation measured with different units? What other units are used to measure radiation?

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What is the difference between sievert, roentgen, and gray? Why is radiation measured with different units? What other units are used to measure radiation?

In: Physics

These aren’t direct measures of radiation, but measures of impacts of radiation. The roentgen is a measure of how much gamma and xray radiation ionises air, but isn’t a measure of anything else. Gray is a measure of how much energy is absorbed by a thing, and is useful in measuring doses of radiation (different things absorb radiation in different amounts, so will receive different doses of radiation even when the amount of radiation you fire at the thing is the same for each). Sievert is a measure of the health effects of radiation, ie, how much damage this much radiation does to people. They’re different units because they measure different things.

Did you watch Chernobyl recently? 🤔

Great question. I’ve always wondered this as well. I’m slightly disappointed that gamma rays’ effect on living tissue isn’t measured in “Banners.”

Bananas can also be used as units for measuring radioactivity. It’s called the BED or banana equivalent dose.

Think of roentgen as a rate of radiation (like litres per hour into a bucket).

Think of sieverts more as a running total (how many liters in the bucket).

Hey, you said ELI5!