Detection of radioactivity — Know

State the main sources that contribute significantly to background radiation.

(a) Radon gas - a radioactive gas released from rocks and soil, present in the air we breathe. (b) Rocks and buildings - some rocks and building materials (e.g. granite) contain naturally radioactive elements. (c) Food and drink - small amounts of naturally occurring radioactive substances are present in what we eat and drink. (d) Cosmic rays - high-energy radiation reaching the Earth's atmosphere from outer space (including the Sun).