Energy that travels from one place to another. Like the heat and light from the Sun! Some types can be harmful, so we need to be careful.

The time it takes for half of a radioactive material to disappear. Like if you start with 100 atoms, after one half-life you'll have 50 atoms left.

A type of radiation made of two protons and two neutrons. It's big and slow, so it can't travel far or go through paper.

A type of radiation made of fast electrons. It can go through paper but is stopped by thin metal.

The strongest type of radiation. Like a very powerful light that we can't see. It can go through most materials but is stopped by thick lead.

When radioactive material gets somewhere it shouldn't be. Like spilling paint on your clothes - but the paint is radioactive!

When something is exposed to radiation. Like getting an X-ray at the doctor - the radiation passes through you but doesn't stay in your body.

How many atoms break down (decay) each second in a radioactive material. Like counting how many raindrops fall per second.

A device that makes clicks when it detects radiation. Scientists use it to measure how much radiation is present in a place.