How does an object become radioactive just by being near or touching something else that is radioactive?
In: Physics
Some basic science to get out of the way: everything is made of 1 or more elements (like iron, gold, oxygen, etc). Elements are made of smaller particles called neutrons, protons and electrons. Each elements has a unique number of each of these subatomic particles.
Generally, radioactive stuff is radioactive because of an imbalance with the number of neutrons or because there are so many subatomic particles (generally only protons and neutrons) that each atom cannot hold itself together too well. Think of it like a stack of blocks. There are only so many blocks you can staack before the tower collapses.
Now, when this collapse inevitebly occurs, the atom in question can either eject 2 of each subatomic particle (alpha decay), just a neutron (beta decay). Generally, the atom also releases a gamma ray with these types of decay.
Now if a normal, non-radioactive atom is close to a redioactive atoms that has just decayed by either of the above methods, it can absorb the decay product. In some cases, this is sufficient to cause an imbalance in the numbers of protons and neutrons. As shown before, this can cause instabilty in the new atom, leading to radioactivity.
Imagine keeping a soccer ball up the air by continuously kicking it. You can’t relax while you have the ball it takes a lot of concentration. You and the ball are “unstable”. Now you kick it off to the person next to you so you can sit down and relax but now that person is juggling the ball and is unstable. Eventually they too will need to kick the ball away.
Imagine you’re at a market and you have a basket filled to the brim with fruit and someone has completely overloaded their basket, causing things to fall out as they move about. Your basket is like a stable particle and theirs is like a radioactive particle – too much stuff/energy in there bursting to get out.
Say an orange falls from their basket into yours as they walk past so now your basket has too many things in it. As you move either the same orange will drop out or something else in your basket will be displaced and fall out instead. Your basket was overloaded because some other nearby overloaded basket dropped something into your already fully-loaded basket, causing yours to have to drop something.
In the case of radiation, instead of fruit and baskets it’s other smaller particles/energy and the center of an atom
Radioactive things are throwing off particles of stuff.
Some times these things hit the center of an atomic nucleus, and get stuck.
Because the thing gets stuck it makes the nucleus more likely to fall apart and send out all it’s things as radiation.
The main thing that gets stuck is a neutron.
A lot of times adding a neutrons to a nucleus makes it more unstable.
Other times a gamma ray photon just whacks it and blow up the nucleus.
Other times it turns a neutron into a proton, making a different element that’s more unstable.
A radioactive substance spews out particles like electrons or neutrons which can make nearby objects radioactive by colliding with them.
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