# Question Video: Sources of Background Radiation

The chart shows how much different sources of radiation contribute to background radiation. Which source contributes the most to background radiation?

03:17

### Video Transcript

The chart shows how much different sources of radiation contribute to background radiation. Which source contributes the most to background radiation?

Okay, so in this diagram, what we see is that we’ve been given a pie chart, so named because it’s a circular chart shaped like a nice delicious pie. Now what a pie chart does is to show the proportional contribution of different objects or groups, or in this particular case sources that contribute to background radiation. In other words, this pie chart will show us all of the different contributors to background radiation, as well as the proportions in which each one contributes to background radiation.

In other words, if the total area of the pie chart represents 100 percent of background radiation, it represents all of the sources that contribute to background radiation. Then in this particular case, we can see that radon gas in the air contributes 41.6 percent of all background radiation. And on the pie chart, that contribution is represented by the blue area. Because the larger the chunk of the pie a particular source takes up, the larger the contribution towards background radiation in this case.

So in simpler words, what this pie chart is telling us is that radon gas in the air contributes 41.6 percent of all background radiation. Food and water contributes 9.6 percent of all background radiation. The ground and the buildings contribute 15.8 percent of all background radiation. Cosmic rays contribute 12.9 percent. Medical sources contribute 19.8 percent. And other sources, which there isn’t enough space to label properly and not enough area on the pie to display as individual sources, contribute to 0.3 percent.

When we add up all the percentages, we add up 41.6 percent to 9.6 percent to 15.8 to 12.9 to 19.8 and 0.3. Those should all add up to 100 percent, which is good because the pie chart is showing us the contribution of each one of these sources to background radiation as a proportion of all background radiation. And so in order to answer this question, we don’t actually even need to know what background radiation is, because all this question is asking us is to find the source that contributes the most to background radiation. In other words, find the source that’s represented on this pie chart as taking up the largest area or having the largest percentage written next to it.

But very quickly, for our peace of mind, background radiation is simply all the ionizing radiation that is present in the environment at a given location. That’s right. All of the environment around us always has some level of background radiation. And this level of background radiation is not harmful to humans. But it’s still important to know about.

But anyway, coming back to our question, the source that contributes the most to background radiation is the one that takes up the largest area of our pie chart. And that happens to be from radon gas in the air, with a massive 41.6 percent of all background radiation being contributed by this source. And we can see that none of the other sources described on this chart have a value as high as 41.6 percent. Because food and water is 9.6 percent, which is less than 41.6 percent. The ground and the buildings are 15.8 percent. Cosmic rays are 12.9, medical sources are 19.8, and other sources are 0.3.

And hence, as the answer to our question, we can say that the source that contributes the most to background radiation is radon gas in the air.