David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.
What is Radiation?
When Bruce Banner gets angry, he turns into the Hulk. This happens due to a hefty dose of gamma radiation. But can radiation really turn you into the Hulk? Is the green glow of radioactivity real? And just what are radioactive substances anyway?
Radiation might sound like something dangerous, but that depends on what kind of radiation you're talking about. There are a lot of different types of radiation: the light coming from a household lamp is a type of radiation, and the microwaves that cook your food are radiation. But when we talk about radioactive substances, we're concerned with particular types of radiation.
A radioactive substance is unstable and produces dangerous kinds of radiation. It is unstable because the strong nuclear force that holds the nucleus of the atom together is not balanced with the electric force that wants to push it apart. Because it's unstable, the atoms will decay into more stable ones.
Another way of thinking about radioactivity is in terms of energy. A radioactive atom has a higher energy than it needs to have. Energy in the universe tends to spread out, and so when something has more energy than it needs, it's only a matter of time until it loses that energy. When a radioactive atom loses its extra energy by decaying, that energy has to go somewhere -- energy in the universe is never created or destroyed, it is said to be always conserved.
Where does it go? It goes into the radiation that is produced. Radioactive substances are continually producing three kinds of dangerous radiation: alpha particles, beta particles and gamma rays. These types of radiation are invisible to the naked eye, and so you don't see a green glow. But sometimes they can interact with nearby phosphorescent or florescent materials that will glow green. This is why a green glow is associated with radioactivity.
Unfortunately for superhero fans, there is no evidence that even these three kinds of radiation can turn you into the Hulk. Radioactive substances produce alpha particles, beta particles and gamma rays. But what are these three types of dangerous radiation?
Alpha particles are the nuclei of helium atoms. They move slowly, don't penetrate the skin, but can cause a lot of damage if swallowed. Beta particles are high-energy electrons that can penetrate through paper and even part of the way into the human body, but cause less damage when they do. And gamma rays are extremely high-energy electromagnetic waves that can only be stopped with thick lead or concrete.
Uses of Radioactive Substances
Let's look at some different uses of radioactive substances.
- Nuclear power plants.
One example of a radioactive substance is uranium. In nuclear power plants, uranium is used to produce electricity. When radioactive substances like uranium produce radiation, they also create a lot of heat. That heat causes water in the power plant to boil, turning turbines and creating electricity.
- Killing Cancer
Radium is another radioactive substance, and is used to treat cancer. Although the radiation produced by radioactive substances can be dangerous, it can also be used to kill cancer cells. A small amount of radium is encased in a gold 'seed' and implanted inside the tumor. This delivers radiation directly to the cancer cells, without destroying other tissues in the body.
- Smoke Detectors
Smoke detectors also contain a radioactive substance: Americium. Packaged inside the smoke detector is a tiny sample of Americium. This Americium produces alpha particles (radiation), which then collides with oxygen and nitrogen in the air to produce ions. Ions are charged particles, and can therefore conduct electricity. These ions allow electricity to flow between two electrodes. But when smoke enters the ion chamber, the smoke particles neutralize the ions and reduce the amount of electricity that flows. When the flow of electricity reduces, the alarm is triggered, and everyone in the kitchen has to cover their ears!
Let's review. A radioactive substance is unstable and produces dangerous kinds of radiation. Radioactive substances produce three types of dangerous radiation: alpha particles are the nuclei of helium atoms. They move slowly, don't penetrate the skin, but can cause a lot of damage if swallowed. Beta particles are high-energy electrons that can penetrate through paper and even part of the way into the human body, but cause less damage when they do. And gamma rays are extremely high-energy electromagnetic waves that can only be stopped with thick lead or concrete. Different uses for radioactive substances include nuclear power plants, cancer treatment, and smoke detectors.
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