I stuck on a documentary about Chernobyl, there was a clip of a pair of boots the fireman were wearing near the plant and the levels of radiation went stupidly high. How can an object like the boots show such a high reading but other objects in the room show lower readings? They also shown a cloth the nurses used on the fireman and the reader did the same thing.
Howcome that happens? Does radiation “stick” to objects?
In: Physics
Edit: I think I got carried away because physics is fun.
tl;dr/more ELI5: Radiation isn’t sticky. Things that emit radiation is sticky because they can be moved around easily by wind and contact. When things come into contact with these things, it is then hard to clean off. If things are not directly subjected to these radioactive things, then they will emit less radiation.
To help understand this, I’ll help define “radiation” first. Radiation in this context refers to all 3 types, named after the first 3 letters of the Greek alphabet: alpha, beta, and gamma. Each are physically different things, and so have different properties when interacting with other matter. There’s also radiation in the form of neutrons, but they’re not *too* different when it comes to this discussion.
Briefly, alpha radiation are ionized helium atoms, beta radiation are electrons, or their anti-matter counterpart, positrons, and gamma radiation is high-energy “light” (electromagnetic waves). All three types are typically labelled as “ionizing radiation” because they contain enough energy to bump into other matter and strip off electrons (to ionize the target atom). This is why ionizing radiation is dangerous, because it will likely cause whatever it comes into contact with to deteriorate in some manner.
Radioactive things are ultimately things that result in these types of radiation, and come from unstable versions of elements (i.e. radioactive isotopes). Because these unstable elements tend to decay and break apart, they release radiation and daughter atoms that may also be unstable themselves, thus causing a chain event of radioactivity.
Now more towards your question. This ability for the detectors to detect radiation levels depends on the amount of ionizing radiation present. The detectors are called Geiger counters (unless there are also other detectors, I’m not a nuclear physics expert), and measure how much stuff inside the detector is being ionized, and correlate that to a level of radiation that would cause that.
So what do we have so far? We have many types of radiation, coming from radioactive elements, which can be detected by Geiger counters. In your example, the boots have a significantly higher radiation reading because they were at reactor trying to put out the fire. As a result, they were subjected to a lot of the crap blown out by the explosion, and were covered/mixed with these radioactive elements. These radioactive elements will then emit radiation, probably in all 3 forms, and is then detected by the Geiger counter.
The room however, was not directly subjected to the dust resulting from the explosion, and thus has less radioactive elements covering the objects in that room. However, this does not mean that it was not subjected it to radiation at all, because there is still the presence of highly-penetrating gamma radiation.
So with that, “radiation” does not stick to objects, it is usually the radioactive elements. These elements are then carried by things that *do* stick to objects, like cement dust, and can result in being rather “sticky” since it cannot be “killed” like a microbe, and all you can really do is wash it off mechanically, or let it decay until it is no longer radioactive. This also helps understand why nuclear fallout is dangerous, because the radioactive materials (effectively “dust”) that come out of an explosion can travel quite far by wind.
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