# Search results

1. ### I Pair production proximity

Does anyone know how close a photon needs to be to a nucleus (an ion really, no shielding from electrons) for pp to occur? I assume it's a probability as a function of distance, any ideas/equations? Thanks
2. ### Refractive index of BEC

Does a BEC still have a very large refractive index for X Ray's and gamma rays?
3. ### Free electron laser weapon -- operating wavelength for the US navy's 1MW FEL?

I know fel operate a wide range of wavelengths, but does anyone know the main operating wavelength for the US navy's 1MW fel?
4. ### Destructive interference at a surface

It's a standing wave, with electric and magnetic field 90 degrees out. When two waves are directed at each other that's what occurs
5. ### Destructive interference at a surface

Sry it is a magnetic standing wave (it does move) but has a node at the mirror
6. ### Destructive interference at a surface

I don't see where there will be constructive interference. At the mirror surface I certainly can't see it, apart from the magnetic fields as they are at an angle to each other and as you make the angle closer to 0 they cancel. however along the beam I can see the electric fields cancelled and...
7. ### Destructive interference at a surface

Is just like when two waves cross over each other and cancel

Why not?
9. ### Destructive interference at a surface

Take two lasers of the same intensity and wavelength and aim them at 30 degrees at the same spot on a mirror, so that at the surface the waves cancel perfectly. What happens? How can the wave be reflected if there is no field present?
10. ### Quantum tunneling instantaneous

http://m.phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html Does this mean that the tunnelling time was actually zero, and the electron 'skips' over the gap, or does it mean that the electron wave travelled at the speed of light followed by an instantaneous jump later on
11. ### Light interaction with charged particles

Does anybody know what happens when say a laser accelerates charged particles? Do photons get absorbed and the intensity of the laser drops, or do they get absorbed and scattered and there's a redshift of the photon etc
12. ### Wave particle duality

Possible that the em wave divides into a range of frequencies, some lower, and these get used for acceleration?
13. ### Wave particle duality

It would have to be Compton/ Thomson scattering, however this is a different process entirely to a charge in an electric field and I don't think you can just neglect the latter
14. ### Wave particle duality

As far as I know, individual photons do diffract. However the question was not do they diffract, but how does the wave cope with running into say, a free electron. It's electric field would accelerate the electron but that would take energy. So obviously the photon isn't sub divided. I can't see...
15. ### Wave particle duality

In the single slit experiment, individual photons may be diffracted. The electric field of the em wave should accelerate charged particles in the screen (if it were a capacitor for example) but only one packet of energy exists. The photon may be absorbed after many wavelengths of light have...
16. ### Accelerating charge emits em waves or pulse

Sry but I don't understand all those hyroglifics. Just intuitively is a free electron similar to an antenna, where I assume a half wavelength pulse can be created or is it a different case
17. ### Accelerating charge emits em waves or pulse

Let me be more specific. An electron in a magnetic field, not synchotron radiation as this is a spiralling electron
18. ### Gravity in particle colliders

What prevents the beam of protons in say the lhc from falling at 9.81 m/s? I've never heard of an electric or magnetic field that prevents it...
19. ### Laser through electron cloud

If the frequency is in the visible I think Thomson scattering would occur, but by how much? Does all of the energy of the incoming wave get absorbed and re emitted by the electron ie Thomson scattered?
20. ### Accelerating charge emits em waves or pulse

Does an accelerating charge, such as one turning a corner emit an em wave or just a pulse? Classical logic dictates it should just be a pulse as there is no oscillation. But which is it?
21. ### Laser through electron cloud

A high intensity continuous wave laser passes through an electron cloud. Please discuss what would happen and in relative amounts. Thanks
22. ### Tokamak particle acceleration

What about the current in the plasma? Doesn't current require motion of charge
23. ### Tokamak particle acceleration

Are these protons and electrons rotating in opposite directions?
24. ### Tokamak particle acceleration

Wel have to wait and see who else replies
25. ### Tokamak particle acceleration

No I mean accelerate. What makes the plasma spin round the tokamak
26. ### Tokamak particle acceleration

In a tokamak design what accelerates the plasma? Is it the current from the primary coils driving the plasma round?
27. ### Laser interaction with ions

Will a laser exposed to ions (doped fibre) spread out in the direction of polarisation as momentum sends the peaks in one direction and the troughs in another. Or, as total momentum is 0 does the wave continue on straight.
28. ### Diffraction limited laser

Why can a laser only be focussed to within its wavelength? It says due to it being diffraction limited, what about focussing lenses and mirrors they don't involve diffraction. Please explain
29. ### Anti hydrogen - hydrogen annihilation

I would like to know what exactly hydrogen and anti hydrogen decay products are. Thanks
30. ### Object falling into the sun

What about this calc A= GM/r^2 A= 10^-11 10^30 / 10^12 = 10^7 That's pretty fast, does this not apply?