# mAs Reciprocity Calculations - Video Lesson

This short video is about a topic that we call mass reciprocity. That's a complicated term for a very simple idea. Remember the formula for calculating mass is actually fairly simple mass is equal to the MA multiplied by the exposure time. As MA increases, the exposure time must decrease in order to maintain the same total exposure. That's the idea of reciprocity. So we can use the balance as an example. On one side, we have the MA And on the other side, we have the exposure time. Resiprocity means that if MA increases by a certain amount the exposure time must decrease by the same amount in order to maintain the same total mass or the same total exposure. So the opposite would also be true. If we double the exposure time, we must decrease the MA by the same amount in order for the total mass to be the same. It's a simple idea, so let's look at a few sample questions of varying complexity. If a radiograph is produced using an MA of two hundred,

## Lesson Quiz

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