27 votes
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Why do X-ray telescopes have to be in space?

X-ray (and gamma rays) are quite penetrating. They can pass through solid matter with much less attenuation than visible light as an example. But that doesn't mean that the attenuation is zero. Put ...
BowlOfRed's user avatar
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24 votes
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What's the difference between Hard X-rays and Gamma-rays?

It can be a little confusing because there are two conventions. The modern convention is to distinguish x-rays from gamma rays by how they are produced. X-rays are produced by electron energy ...
PM 2Ring's user avatar
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20 votes

Why do X-rays go through things?

You have to distinguish, which interactions take place, when electromagnetic radiation passes through a solid and interacts with it. There is a nice plot on Wikipedia, showing the dielectric response ...
engineer's user avatar
  • 2,305
17 votes

Why don't X-rays penetrate the bone?

Bones absorb more xrays than soft tissue because of the Calcium in the bones (and the high density helps too, but the same densities of, say, Carbon or Silicon, wouldn't absorb as many x-rays). The ...
tom10's user avatar
  • 2,847
13 votes

Why do X-rays go through things?

Light is composed out of a large ensemble of photons, and photons are quantum mechanical elementary particles. Matter is composed out of atoms and molecules , which have small dimensions and are in ...
anna v's user avatar
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10 votes

Computers That Can Compute in Femtoseconds

There is a lot of confusion in this question. Let me try to clear up some of it. First, the LCLS II is not yet running. The LCLS II is expected to begin operation in 2022. However, SLAC is doing ...
Michael Peskin's user avatar
8 votes
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Medical X-Ray - why no diffraction?

Since the lattice spacing is about eight angstroms, the issue isn't any sort of unusual lattice spacing. Instead, the issue is that bones are thick. [Another answer points out that the crystals are ...
rob's user avatar
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8 votes

X-ray image of the Earth

This experiment has sort-of been done. As far as I know, no X-ray satellite has captured an image of the Earth eclipsing the Sun, but HINODE observed an eclipse of the Sun by the Moon at X-ray ...
ProfRob's user avatar
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8 votes

Why do X-ray telescopes have to be in space?

To extend very slightly upon BowlofRed's answer: X-ray photons interact with electrons. More electrons in an atom means more interactions, and more interactions means less penetration. In general ...
niels nielsen's user avatar
8 votes

Why do X-ray telescopes have to be in space?

Is water transparent? It seems so in a glass, but a kilometer of water is nearly opaque. The deep ocean is dark. Air at atmospheric pressure is similarly opaque to x-rays on a kilometer scale. It's ...
John Doty's user avatar
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7 votes
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How large should an optically large fusion reactor be?

I think that this is an interesting question and I will try to give a very rough answer (warning: it might include some approximations). Instead of calculating the optical thickness of the D-T plasma,...
Alf's user avatar
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7 votes
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Recombination of protons in solar wind

First, look at https://physics.stackexchange.com/a/288810/59023 for recombination rate info and https://physics.stackexchange.com/a/695956/59023 for radial dependence of temperatures in the solar wind ...
honeste_vivere's user avatar
6 votes
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Units used in X-ray energy spectrums

I think the way to read your "hash" ("#") is as "number." What you've plotted here is a differential spectrum: the number of x-ray events observed in each energy window from $E_i$ to $E_i + \Delta E$....
rob's user avatar
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6 votes
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Can X-rays emitted due to bremsstrahlung radiation have frequency matching with other EM waves like visible ones?

The continuous X-ray spectrum comes from Bremsstrahlung radiation, which is the radiation emitted whenever an electric charge is accelerated or decelerated. In this case electrons striking the metal ...
John Rennie's user avatar
6 votes
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Where is the 2.05 MJ input energy measured? (referring to the recent experiment at the National Ignition Facility (NIF))

Where exactly is the 2.05 MJ measured? It's the amount of UV light entering the target chamber. The reason for this particular measure is primarily historical. Note that LLNL has, on occasion, ...
Maury Markowitz's user avatar
5 votes
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Continuous X-Ray spectrum

When electrons hit a solid, they are abruptly decelerated. They don't lose all their energy at once - they lose a certain amount with each "collision" or near-collision with particles (...
Floris's user avatar
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5 votes
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K alpha and K beta, which one has more energy?

The $K_\alpha$ is produced by the $2p \to 1s$ transition and the $K_\beta$ is produced by the $3p \to 1s$ transition. So the $K_\beta$ radiation has a higher energy than the $K_\alpha$ transition. If ...
John Rennie's user avatar
5 votes
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Refraction of X-rays

My question is, how are x-ray images able to be produced if the x-rays refract as they pass from air into the body and then back into air? Short Answer X-ray images give us information about the ...
Thomas Lee Abshier ND's user avatar
5 votes

X-ray image of the Earth

X-rays work by being absorbed in denser material, producing the shadow that is the traditional X-ray image. Medical X-rays are designed to top out looking at calcium-40 ($Z$=20). On an object the size ...
JEB's user avatar
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5 votes
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Are there solid-state devices that can produce x-rays?

The problem is what mechanism can you use to produce X-Rays with solids... atomic or molecular, band transition, whatever you use in solids do not enter the X-Ray regime when it comes to produce high ...
Nelson Vanegas A.'s user avatar
5 votes
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What is the wavelength range of X-rays?

Breaking up the electromagnetic spectrum into discrete bins (x-rays, microwaves, radio waves, ...) is a tool which makes thinking about electromagnetic radiation easier. Putting hard limits on what ...
J. Murray's user avatar
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4 votes

Why we don't use gamma rays, x-rays or ultraviolet to transmit data?

Actually, NASA and others are considering the use of X-rays as a communication medium. The difficulty comes in the modulation, and in the fact that X-rays can't be transmitted via wires or fiber. But ...
Deirdre Hebert's user avatar
4 votes
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What happens if positrons, instead of electrons, are decelerated inside an X-ray tube?

I would say there will be a huge effect. I am not sure if acceleration vs. deceleration is very important, but there will also be gamma radiation due to annihilation of the positrons with electrons of ...
akhmeteli's user avatar
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4 votes
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X-ray Lasers and Forbidden Transitions

As mentioned in Semoi's answer, electronic transitions in the x-ray regime have the disadvantage that they will tend to be ionizing transitions, i.e. they will put one electron in the continuum, where ...
Emilio Pisanty's user avatar
4 votes
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How can a monochromatic X-Ray tube produce a spectrum in XPS?

Because the X-rays, in the Photoelectron spectroscopy device, excite the electrons from the individual core levels out and as we know the electrons from the individual core levels reside in different ...
ubuntu_noob's user avatar
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4 votes

What is ptychography, in a nutshell?

Ptychography is a high resolution imaging technique. In standard microscopy light goes through a sample where it is absorbed and refracted, followed by a lens to form an image. In diffractive imaging ...
stefano's user avatar
  • 359
4 votes
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Why are soft x-ray images of plasmas considered to represent magnetic field line configurations?

The X-rays come from charged particles (ions and electrons), both continuum (bremsstrahlung) and discrete transitions contribute (i.e. continuum radiation from free-free and free-bound processes, and ...
ProfRob's user avatar
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4 votes
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Is the Compton effect observed during regular x-ray diffraction?

Yes, in fact Compton scattering is often an annoyance in x-ray diffraction when you want to study the diffuse background from crystal defects and disorder. The amount of Compton scattering is highly ...
KF Gauss's user avatar
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