One reason radiation is dangerous is that it can’t be detected with the senses. You normally can’t see it, smell it, hear it, or feel it. Fortunately, there are devices such as Geiger counters that can detect radiation. A Geiger counter, like the one in Figure below , has a tube that contains atoms of a gas. If radiation enters the tube, it turns gas atoms to ions that carry electric current. The current causes the Geiger counter to click. The faster the clicks occur, the higher the level of radiation.
A scientist is doing a study in his lab about the radioactivity of some rocks that he found on an expedition. He colored the two different rocks to be able to tell them apart; one Red, and one Blue. He is using a Geiger counter to measure them, and finds that the Red rock causes the Geiger counter to click rapidly, and the Blue causes almost no clicks.
Does the Blue rock have a higher or lower radioactivity than the Red rock?