Can a beam of photons accelerate an atom or object?

In summary, photons can increase the energy level of an electron in an atom, which can then be used to accelerate the atom. This is what light pressure does to an object.
  • #1
PJMath
2
0
Not quite sure how to ask this, but here goes: I think I understand how a photon impacting an atom can increase the energy level of an electron in the atom. When I read about "light pressure", I thought, is there a way for, say, a stream of photons to accelerate an atom by continually impacting the atom until it moved or changed its velocity? Is this what light pressure does to an object? Thanks for any insights.
 
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  • #2
PJMath said:
Not quite sure how to ask this, but here goes: I think I understand how a photon impacting an atom can increase the energy level of an electron in the atom. When I read about "light pressure", I thought, is there a way for, say, a stream of photons to accelerate an atom by continually impacting the atom until it moved or changed its velocity? Is this what light pressure does to an object? Thanks for any insights.
Yes, "light sails" do move things because light has momentum even though it has no mass
 
  • #4
https://upload.wikimedia.org/wikipe...s_radiometer.jpg/220px-Crookes_radiometer.jpg
220px-Crookes_radiometer.jpg
 
  • #7
PJMath said:
Not quite sure how to ask this, but here goes: I think I understand how a photon impacting an atom can increase the energy level of an electron in the atom. When I read about "light pressure", I thought, is there a way for, say, a stream of photons to accelerate an atom by continually impacting the atom until it moved or changed its velocity? Is this what light pressure does to an object? Thanks for any insights.

Charged particles, including heavy ions, are accelerated in particle accelerators using RF fields. So that, technically, are photons.

Zz.
 
  • #8
jtbell said:

Very interesting, thanks! I definitely had the wrong picture in my head about how it worked.

  1. The final piece of the puzzle, thermal transpiration, was theorized by Osborne Reynolds[5] in an unpublished paper that was refereed by Maxwell, who then published his own paper which contained a critique of the mathematics in Reynolds's unpublished paper.[6] Maxwell died that year and the Royal Society refused to publish Reynolds's critique of Maxwell's rebuttal to Reynolds's unpublished paper, as it was felt that this would be an inappropriate argument when one of the people involved had already died.[3] Reynolds found that if a porous plate is kept hotter on one side than the other, the interactions between gas molecules and the plates are such that gas will flow through from the cooler to the hotter side. The vanes of a typical Crookes radiometer are not porous, but the space past their edges behaves like the pores in Reynolds's plate. On average, the gas molecules move from the cold side toward the hot side whenever the pressure ratio is less than the square root of the (absolute) temperature ratio. The pressure difference causes the vane to move, cold (white) side forward due to the tangential force of the movement of the rarefied gas moving from the colder edge to the hotter edge.[3]

But so are they saying that with a fully evacuated version that has mirrors on the vanes, that you won't get rotation if you shine a strong laser on one side of one of the vanes? I suppose that the small vane pivot friction is too big to overcome with just light (as opposed to a solar sail in frictionless space)...
 
  • #9
anorlunda said:
Definitely yes. This is the key principle of the two-stage thermonuclear warhead, radiation pressure up to 1,400 million bars!

You may also have seen news about the lightsail project last week.
https://en.m.wikipedia.org/wiki/Thermonuclear_weapon#Radiation_pressure
Thanks for the response. Can you also recommend any books/articles/etc. that I can read to obtain a better understanding of this topic? For example, at what point or energy level might a stream of photons go from simply heating up an object to affecting its velocity?
 
  • #10
PJMath said:
Thanks for the response. Can you also recommend any books/articles/etc. that I can read to obtain a better understanding of this topic? For example, at what point or energy level might a stream of photons go from simply heating up an object to affecting its velocity?

Ah, you may need to reprase your question. The literal answer is and and all energy levels. I think you're getting hung up on unscientific notions of "significant" heating and "significant" velocity change.
 

1. Can a beam of photons accelerate an atom or object?

Yes, a beam of photons can accelerate an atom or object. This is due to the fact that photons carry energy and momentum, and when they interact with an atom or object, they can transfer some of that energy and momentum, causing it to accelerate.

2. How does a beam of photons accelerate an atom or object?

When a photon interacts with an atom or object, it can either be absorbed or scattered. If it is absorbed, the energy and momentum of the photon is transferred to the atom or object, causing it to accelerate. If it is scattered, the change in momentum of the photon can also result in an acceleration of the atom or object.

3. Is the acceleration caused by a beam of photons significant?

The acceleration caused by a beam of photons may be significant depending on the energy and intensity of the beam, as well as the mass of the atom or object. In some cases, it may be too small to measure, while in others, it may be enough to cause noticeable effects.

4. Are there any limitations to the acceleration caused by a beam of photons?

Yes, there are limitations to the acceleration caused by a beam of photons. The acceleration will only occur in the direction of the beam, and the maximum acceleration will depend on the energy and intensity of the beam, as well as the size and composition of the atom or object.

5. Can a beam of photons accelerate an atom or object indefinitely?

No, a beam of photons cannot accelerate an atom or object indefinitely. Eventually, the energy and momentum of the photons will be depleted, and the acceleration will cease. Additionally, factors such as air resistance or other external forces may also affect the acceleration and eventually bring it to a stop.

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