For most of the sources you encounter in on a regular basis life, the quantity of radiation is so low that you simply don’t want to fret about it. However ionizing radiation will also be harmful, as a result of these free electrons work together with the molecules within the cells and tissues of the human physique. Including an additional electron can break the chemical bonds that maintain molecules collectively. That’s the reason the radioactive substances related to nuclear weapons and energy plant meltdowns can increase the danger of most cancers.
There are 4 kinds of ionizing radiation: alpha, beta, gamma, and neutron radiation. Right here’s what is going on on with every kind and the way they are often detected.
Alpha Particles
In 1896, nobody actually knew something about radiation. They did not know if it was a particle or some kind of electromagnetic wave, like mild. So that they determined to make use of the time period “rays” within the generic sense—like mild rays. That’s how we get holdover phrases like alpha rays or gamma rays.
However—SPOILER ALERT—alpha rays are usually not waves. They’re really electrically charged particles. An alpha particle is fabricated from two protons and two neutrons. Which means an alpha particle is a helium atom with out the electrons. (Sure, they need to have known as them “helium particles,” however nobody knew what was happening.)
How are you going to inform that it’s alpha radiation, and never another kind? The reply is that alpha particles can simply be blocked by one thing as skinny as a sheet of paper. So when you’ve got a supply that produces alpha particles, you possibly can protect the detector—like photographic movie—with a really small quantity of fabric.
The explanation that alpha particles are so simply blocked is that, as a result of they’re so heavy, they’re typically ejected from the radioactive supply with a comparatively sluggish pace. Additionally, with {an electrical} cost equal to 2 protons, there’s a important electrostatic drive between the alpha particle and the optimistic nucleus of the shielding paper. (We name this a cost of 2e, the place e is the basic cost of an electron or proton.) It would not take too many of those atoms within the paper to basically carry the alpha particle to a cease.
Have you learnt what else can cease an alpha particle? Human pores and skin. That’s why alpha radiation is commonly thought of to be the least dangerous of the radiation sorts.
Beta Particles
In 1899, Ernest Rutherford labeled three kinds of radiation: alpha, beta, and gamma. Whereas the alpha particles have been simply stopped, beta and gamma particles might undergo some quantity of metallic shielding, penetrating additional into materials as a result of they’re much decrease mass. The truth is, beta particles are electrons—the basic particles with a destructive cost. The mass of an alpha particle is greater than 7,000 instances bigger than that of a beta particle. Which means very low-mass beta particles may be emitted with very excessive speeds that give them the power to penetrate objects, together with the human physique.
Gamma Rays
Gamma rays are literally rays, not particles. They’re the third class of radiation, and a kind of electromagnetic wave—similar to seen mild.
Nevertheless, the sunshine that you may see along with your eyes has a wavelength between 400 and 700 nanometers, whereas gamma rays have a a lot smaller wavelength. A typical gamma ray might need a wavelength of 100 picometers. (Word: 1 picometer = 10-12 meter, and 1 nanometer = 10-9 meter.) Which means the wavelength of gamma radiation may be round 1,000 instances smaller than seen mild. With such a small wavelength, and a really excessive frequency, gamma rays can work together with matter at very excessive vitality ranges. They’ll additionally penetrate fairly deep into most supplies, so it normally takes a big chunk of result in block this radiation.