# Questions about light

Discussion in 'Physics & Math' started by jcc, Jul 24, 2015.

1. ### James RJust this guy, you know?Staff Member

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jcc:

To interact with some atoms, the laser light must be at a frequency at which it will be absorbed by the atoms. A suitably-tuned laser will interact with smoke particles or a flame.

Where did you read that "the strongest laser beam cannot bend flame or move smoke"? Or is this based on your own experience in some way?

Laser light can be affected by electromagnetic fields - particularly its polarisation.

An electric field or a magnetic field alone will not bend a laser beam because, as paddoboy said, the laser beam does not contain any charged particles.

A laser that melts steel is absorbed by the steel. The same light will not necessary be absorbed by a diffuse gas such as in smoke or a flame.

Electromagnetic waves have no charge either. Photons are essentially electromagnetic waves (in quantised packets).

In the photoelectric effect, an incoming photon must have a frequency suitable to lift an electron out of one of the occupied energy levels of the metal that it is falling on. If the photon frequency is too low, nothing happens. When a photon ejects an electron, the photon is absorbed by the electron and its energy goes partly to removing the electron from the metal, with any excess ending up as kinetic energy of the ejected electron.

It is not the impact of the photons that cuts the steel. It is the depositing of the energy of many photons in the metal, causing it to heat and eventually melt.

Yes, but only if the photon frequency is just right so that the flame atoms can absorb the light.

This effect is the principle by which laser cooling of diffuse atoms works, by the way. Bose-Einstein condensation relies on exactly the effect of absorption of photons by a diffuse gas that you are describing.

Hope this helps!

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3. ### jccRegistered Senior Member

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Thank you for the answers. I am not agree at all.

If sunlight able to sail spaceship, why is laser beam not able to bend a flame? Isn't photon has momentum?

The plasma on the sun's surface has no electron to change orbitals, why still emit light?

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5. ### Dr_ToadIt's green!Valued Senior Member

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Wasn't your grammar a little better than this before your last temporary ban? Not to mention your reading comprehension..

Are you channeling Marosz or something?

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7. ### exchemistValued Senior Member

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Nah this troll uses a fake persona, I suspect. My guess is it is a strain trying to keep up exactly the same degree of bad English all the time and that the mask slips occasionally

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8. ### originHeading towards oblivionValued Senior Member

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That's too bad since your disagreement is based on ignorance.
This has been explained to you few times. Why don't you point out what you specifically disagree with in the answers already given.
This has been explained to you few times. Why don't you point out what you specifically disagree with in the answers already given.
This has been explained to you few times. Why don't you point out what you specifically disagree with in the answers already given.

9. ### originHeading towards oblivionValued Senior Member

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We should set up a pool and bet on how long it will be until his next ban. I think the time frame will have to be in hours and not days.

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10. ### exchemistValued Senior Member

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Well you were right. He's gone forever, at last.

Thank you Mods. What a blessed relief.

11. ### paddoboyValued Senior Member

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Our relief will no doubt be to someone else's/science forum's annoyance.

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12. ### James RJust this guy, you know?Staff Member

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All the evidence supports what I say and none of it supports what you say. Your agreement or disagreement doesn't matter, unless you can persuade other people that you are right and they are wrong.

I already answered this question above. If you require clarification, please ask a more direct question.

Highly energetic particles can exchange energy in many ways. One way is to emit or absorb light.

13. ### exchemistValued Senior Member

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Yeah, but anywhere else he'd get banned within about 5 minutes.

14. ### Dr_ToadIt's green!Valued Senior Member

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And IP blocked.

What ever happened to that feature that is supposed to prevent trolls from posting in the science fora?

15. ### sweetpeaValued Senior Member

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Would I be correct in saying... the electrons in a plasma 'emit' photons when accelerated by the EM field of the sun?

Last edited by a moderator: Aug 3, 2015
16. ### Walter L. WagnerCosmic Truth SeekerValued Senior Member

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Yes. A change in velocity for an electron (an electro-magnetic disturbance is what that's called) will be accompanied by an electromagnetic emission; i.e. a photon. This is generally true, unless the electron is in a 'bound' state, such as around a positive charge (e.g. a proton or positron), in which case its quantum state precludes emissions (unless dropping from one higher quantum state to a lower one, which is usually termed x-ray emission; or absorbing a photon and going to a higher quantum state).

Last edited: Aug 4, 2015
17. ### brucepValued Senior Member

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4,098
Good doctor toad. You're the expert. What can you do with the function 'you can't start a thread until you reach some set number of posts'. IE could you stop certain folks from starting a thread based on something other than a minimum number of posts?

18. ### Dr_ToadIt's green!Valued Senior Member

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I don't know how XenForo works, but most software packages have some sort of permission system that can be triggered on a counter or an admin flag, and configured on a per-group basis, or as granular as a per-user level.

Sorry if I ran on.

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