Questions tagged [radiation]

Radiation is a process in which energetic particles or energetic waves travel through a medium or space. The particles or waves radiate (i.e., travel outward in all directions) from a source.

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Why is nuclear waste more dangerous than the original nuclear fuel?

I know the spent fuel is still radioactive. But it has to be more stable than what was put in and thus safer than the uranium that we started with. That is to say, is storage of the waste such a big ...
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87 votes
3 answers
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Why can Hiroshima be inhabited when Chernobyl cannot?

There was an atomic bomb dropped in Hiroshima, but today there are residents in Hiroshima. However, in Chernobyl, where there was a nuclear reactor meltdown, there are no residents living today (or ...
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75 votes
5 answers
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How does an ordinary object become radioactive?

In the 2019 miniseries "Chernobyl", ordinary objects are depicted as being capable of becoming radioactive, such as clothes, water, stones. How exactly does something composed of a non-radioactive ...
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45 votes
16 answers
9k views

Why is radioactive half-life constant?

Say you have just four radioactive atoms with a half-life of one hour. (I am using a small number of atoms to keep it simple and illustrate my confusion more clearly). So that means one hour from now, ...
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41 votes
7 answers
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Do nuclei emit photons?

Generally in text books they say that when a electron goes from high energy state to a lower energy state it emits photons. My question is, it is possible that a proton that goes from high energy ...
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36 votes
4 answers
4k views

The problem of self-force on point charges

Allow me to preface this by stating that I am a high school student interested in physics and self-studying using a variety of resources, both on- and off-line, primarily GSU's HyperPhysics website, ...
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29 votes
4 answers
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What is wrong with my setup of cloud chamber?

My setup: plastic box (~1l) with the cover painted black mat the bottom of the box covered with sponges saturated with ethyl alcohol (90%) to the limit (all over sponge capacity poured back to bottle)...
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28 votes
6 answers
4k views

How is Alpha Radiation possible?

Alpha radiation would seem to occur when a pair of protons and neutrons are magically plucked from the amorphous (i.e. having no particular structure) nucleus of a heavier atom. Some of the problems ...
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28 votes
6 answers
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Is a suit that hides a soldier's heat signature fundamentally possible?

I recently played "Crysis", a game where the protagonist wears a suit that allows the player to hide both himself and his heat signature. Then I watched Iron Man 3, where a kid suggests that Tony ...
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27 votes
2 answers
13k views

Is it safe to keep uranium ore in my house?

I bought 5.6 gr of uranium ore. The measured gamma radiation is 1µSv/h, we didn't have the instruments to measure alpha/beta radiation. EDIT: The gamma radiation was measured at 1cm distance. I also ...
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25 votes
4 answers
6k views

Decay of massless particles

We don't normally consider the possibility that massless particles could undergo radioactive decay. There are elementary arguments that make it sound implausible. (A bunch of the following is ...
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23 votes
2 answers
10k views

Why is the graphite moderator in a nuclear reactor radioactive?

Some nuclear reactors (like the RBMK in Chernobyl) use graphite as a neutron moderator. As far as I understand, this graphite material, either in rods or as blocks with embedded channels, surrounds ...
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22 votes
4 answers
158k views

What exactly is the difference between radiation, conduction, and convection?

Okay, so everywhere I've read, I hear the main difference is the requirement of a medium. But for example, if you take the case of heat 'radiating' from a red-hot iron, isn't that actually convection ...
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22 votes
2 answers
24k views

Why doesn't the evening/morning sun feel much hotter on your face?

I understand that places on the Earth's surface get hotter in summer, and in the middle of the day rather than morning or evening, because the surface of the Earth is presented 'face-on' to the Sun at ...
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22 votes
4 answers
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Why are alpha particles such a prominent form of radiation and not other types of nucleon arrangement?

It is said in many textbooks that alpha decay involves emitting alpha particles, which are very stable. Indeed, the binding energy (~28.3 MeV) is higher than for $Z$-neighboring stable isotopes. But ...
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21 votes
3 answers
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Should Beta Minus decay put an upper limit on the mass of a neutrino?

Beta minus decay emits an electron with a range of energies. Within the nucleus, the following is happening: $n\rightarrow p+e^-+\bar{v}_e$. For this reaction to be possible, by lepton number ...
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21 votes
2 answers
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In $_6^{14}\mathrm C$ decay, how is mass-energy conserved?

The mass of a carbon 14 atom is $14.003\,241\,988\,7\:\mathrm{u}$, nitrogen 14 has a mass of $14.003\,074\,004\,78\:\mathrm{u}$, and the rest-mass of an electron is $0.000\,548\,579\,9\:\mathrm{u}$ ...
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21 votes
2 answers
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Why doesn't orbital electron fall into the nucleus of Rb85, but falls into the nucleus of Rb83?

Rb83 is unstable and decays to Kr-83. Mode of decay is electron capture. Rb85 is stable. The nuclei Rb83 and Rb85 have the same charge, but Rb85 is heavier than Rb83. While gravity acts more strongly ...
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20 votes
3 answers
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Can two spaceships go fast enough to pass straight through each other?

Probability of interaction between two particles tends to wane with increasing energy. Technically, the cross section of most interactions falls off with increasing velocity. $$\sigma(v) \propto \...
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19 votes
5 answers
45k views

How do electrons jump orbitals?

My question isn't how they receive the energy to jump, but why. When someone views an element's emission spectrum, we see a line spectrum which proves that they don't exist outside of their orbitals (...
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19 votes
2 answers
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Where is radiation density in the Planck 2013 results?

I've been looking at the Planck 2013 cosmological parameters paper, trying to update my toy cosmology simulator with the most recent data. Most of the interesting values such as $H_0$, $\Omega_m$, ...
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19 votes
1 answer
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How hot would tritium water be?

I realize this is kind of a silly question, but if you have tritium water, with the tritium half life of 12.5 years, I expect it would be quite hot. (note, this is not a homework question, I'm just ...
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19 votes
2 answers
443 views

In the Iranian nuclear deal, how can IAEA detect nuclear activity after 24 days?

This is a question related to current events, but I want to ask about the physics, which are not explained in any news article that I can find. Ernest Moniz and John Kerry wrote an op-ed in the ...
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17 votes
4 answers
5k views

What exactly does the weak force do?

I know that the weak force acts on nuclei and causes decay. But what exactly does the weak force do? Or to put it another way, why do we call it a force? Does it push the red particle of the picture ...
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17 votes
4 answers
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Why aren't betavoltaics and alphavoltaics batteries widely used?

Betavoltaic batteries are devices which creates electricity from beta radiation of a radioactive material. Alphavoltaics operate similarly, using alpha radiation. The concept was invented roughly 50 ...
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16 votes
6 answers
3k views

Why can I see the top of objects in a reflection when they are not facing the reflective surface?

Why am I able to see the top of the pictures even though they aren’t facing the reflexive surface. The light would have to travel down through the picture
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  • 502
16 votes
3 answers
3k views

Where do gamma ray photons come from?

I'm a layman interested in learning more about nuclear radiation. Heavy elements like plutonium or uranium will eject protons and neutrons as alpha particles, electrons as beta particles, and photons ...
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16 votes
6 answers
6k views

Can UV light make us invisible?

For an object to create different EM waves, it needs to increase the temperature, so what if we or some material could be so hot, that it would emit ultraviolet light, and thanks to that be invisible ...
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16 votes
3 answers
4k views

Is it possible to avoid the radiation that caused the American flag turned into white on the Moon? [closed]

While lunar images have proven that the American flags planted during the Apollo missions are still standing on the moon, lunar scientists have now said that they probably no longer hold the iconic ...
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16 votes
2 answers
3k views

How to detect a secret nuclear detonation here on the earth?

How can we know that North Korea and Iran (to name a few) are exploding nuclear weapons if no inspectors have ever been granted access to suspected nuclear sites in these countries? How can we ...
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16 votes
3 answers
2k views

What did recombination look like?

I recently remembered that someone worked out what the big bang sounded like and that got me thinking... About 377,000 years after the Big Bang, electrons became bound to nuclei to form neutral atoms....
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16 votes
2 answers
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How does quantization solve the ultraviolet catastrophe?

I understand how classical physics leads to the UV catastrophe. But I cannot understand how quantization solves it. How can quantization prevent the body from radiating a lot of energy? I know this ...
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15 votes
2 answers
10k views

Why are alpha particles made of 2 protons and neutrons?

When experiencing alpha decay, atoms shed alpha particles made of 2 protons and 2 neutrons. Why can't we have other types of particles made of more or less protons?
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15 votes
5 answers
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What common materials absorb most infrared light?

I'm competing in a simple robotics competition where most of the participants use reflected infrared light to detect their opponent. I'd like to make my own robot as difficult to see as possible. What ...
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15 votes
3 answers
3k views

What temperature can you attain with a solar furnace?

A solar furnace is a device that concentrates the sun's light on a small point to heat it up to high temperature. One can imagine that in the limit of being completely surrounded by mirrors, your ...
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14 votes
5 answers
3k views

What triggers a nuclear decay?

I am not a physicist but I have been wondering about this: I understand that the decay of a nucleus is a random event and one cannot predict exactly when it will happen for a particular nucleus. ...
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13 votes
3 answers
3k views

How much radiation do nuclear physics experiments expose researchers to nowadays?

I am curious about how much radiation do experimental nuclear physics researchers/students suffer in nowadays research environment. I know this may be a dumb question, but I have can found answer ...
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13 votes
2 answers
2k views

Is an alpha particle four nucleons or dodecaquark?

In a $\alpha$ particle, do the 4 nucleons stay distinct in any meaningful manner, or is it more accurately considered to be a hadron composed of 12 valence quarks that are not subdivided into nucleons?...
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13 votes
2 answers
12k views

Why is the spectrum of the $\beta$-decay continuous?

the spectrum of the Gamma and Alpha decays are both discrete, i.e. the $\alpha$-particles and the $\gamma$-rays take on only discrete values when emitted from a decaying nucleus. Why is it then, that ...
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13 votes
6 answers
2k views

Is there any thing other than time that "triggers" a radioactive atom to decay?

Say you have a vial of tritium and monitor their atomic decay with a geiger counter. How does an atom "know" when it's time to decay? It seems odd that all the tritium atoms are identical except with ...
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13 votes
2 answers
7k views

What Happens to electrons after Alpha Decay and Nuclear Fission?

Where do the electrons go? In alpha decay do 2 electrons follow the alpha particle and make stable Helium or does the larger daughter nucleus become an anion? Also what do the electrons do in the ...
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13 votes
2 answers
32k views

Why do microwave ovens use radiation with such long wavelength?

According to Wikipedia: Consumer ovens usually use 2.45 gigahertz (GHz)—a wavelength of 12.2 centimetres (4.80 in). Typically, I put the dish inside the oven in its center. I suspect most people ...
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13 votes
5 answers
581 views

$\beta^+$ decay

We've been discussing radioactive decay at school, and I grasped everything except for $\beta +$ decay. When I googled radioactive decay, I immediately found out they dumbed down radioactive decay for ...
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13 votes
3 answers
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Why some nuclei with "magic" numbers of neutrons have a half-life less than their neighbor isotopes?

It's easy to find the "magic" numbers of neutrons on the diagrams of alpha-decay energy: 82, 126, 152, 162. Such "magic" nuclei should be more stable than their neighbors. But why some nuclei with "...
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12 votes
5 answers
2k views

Fundamentally, why do some nuclei emit ionizing radiation?

I understand that some nuclei and their isotopes are not stable and therefore at random intervals bits of the nucleus (i.e. protons & neutrons) break away with differing amounts of energy ...
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12 votes
3 answers
55k views

Would being underwater help survive a nuclear bomb?

If I jump in my pool, on the river near my house knowing that a nuclear bomb, or atomic or H-Bomb exploded around 10 km from my house, would I survive? The way I see it is that water will protect me ...
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12 votes
2 answers
11k views

What is the temperature of the clear night sky from the surface of Earth?

Before you all jump in with 2.73 K or thereabouts, this is more of an experimental question. It will obviously depend on humidity and radiation being scattered back towards the surface of the Earth. ...
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12 votes
4 answers
4k views

What is happening over the 15 minutes it takes a neutron to decay?

I've read that free neutrons decay into a proton, electron and neutrino with an average lifespan of about 15 minutes. Is there anything physically different about a neutron that has existed for 14 ...
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12 votes
3 answers
637 views

Does neutron radiation form clouds?

I've heard a couple of scary stories from experienced accellerator physiscists about something called neutron clouds. Apparently, if you have an experiment like a fixed-target experiment that produces ...
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  • 3,957
12 votes
2 answers
407 views

Why can't a massive particle decay to a lesser mass and a photon?

I want to calculate a process $M \to \gamma ~ m$ where m is a lesser mass state and M is a heavier state. Going through the Feynman diagram I get a matrix element ${\cal{M}}^2=2g^2(~(M-m)^2-2mM)$, but ...
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