Light travels in the form of a wave.It has masless photons travelling at the speed of light.Does it mean that tha photons travels in the trajectory same as that of a wave.
19930
At the end of this nice video (), she says that  is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward.  I wonder where the  is in this explanation. What is the relation between electromagnetic wave and photon?
26571
I'm a newbie with physics but I'm wondering how a ray of light can essentially be represented. I have always known that a ray of light proceeds in a straight line until it encounters another object (or material) that refracts/reflects it. But a light ray should be part of an electro-magnetic wave, is this correct? If it is so, it should obey to the  and this doesn't seem to me to describe a straight line ray.  I'm having problems visualizing how light is emitted and how it relates with the wave equation. Can someone with a clear understanding of the problem explain it to me in simple terms?
2134
Yesterday I read that we can affect the path and the 'form' (particle or wave) of a photon after the fact ().  Part of what is puzzling me is the beam-splitter. Are the individual photons actually being split into two new photons of lesser energy?  This  implies that you cannot split a photon but it seems that beam splitters do exactly that.
22168
How does light travel, does this not contradict the idea that going the speed of light stops time? Because if going the speed of light stops time and light goes the speed of light shouldn't it be dark?
69880
As a student in a highschool physics class, my teacher has repeatedly told me that photons are massless. Yet, I have also heard from other sources that photons have momentum. If photons were to have momementum, that would mean that they have mass as according to p = mv.  Do photons really have mass?  Also, how would this mass be calculated?
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I was wondering why a laser beam diverges. If all the photons are in the same direction, I would imagine that it would stay that way over a long distance. I am aware that a perfectly collimated beam with no divergence cannot be created due to diffraction, but I am looking for an explanation based on  photons rather than wave physics.
25630
whenever two media and two velocities are involved, one must follow Snell's law if one wants to take the shortest time.   Why snells law must be followed to travel diffrent media in shortest time?  Does this mean that the path followed by light in travelling through different media will give a straight line if different media are transformed into like first media? I think so because one would get shortest time if one travel in a straight line.  So how does this apply to particles? Does this statement points wave particle duality?
61414
I'm just a layman with no real science background  (a) I'm not really sure what a shadow is. Some people are saying that it's the absence of something (a photon?) and therefore it is not subject to laws of physics. But I know when I'm in a shadow and when in sunlight... that's "information", and I thought that information flow can't break the speed of light limit.  (b) Some others use the laser pointer/flicking wrist example to talk about laser dots moving faster than light speed. But that can't be right, can it? The photons from the laser point have to travel from A to B and (after wrist flick) from A to C ... but the photons are all moving at the speed of light - there's no law-breaking in moving the laser dot from point B to point C because the photons are moving either from A to B or A to C ... the distance from B to C is not material (is it?).  (c) Also, can a shadow be thought of as a gap in a photon flow? E.g. if I interrupt a beam of single photons then can I think of it as e.g. PPPSSSPPPSSSPPPSSSPPP, etc where P = photons and S(shadow) = no photon &amp;, if so, the "SSS" is effectively travelling at the speed of light ... no faster.
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I'm reading some texts that seam to assume knowledge of light that I'm not too familiar with. How does wavelength of light relate to the minimum distance span that can be observed (i.e. you cannot make a lens big enough to resolve individual atoms), and is this a light phenomena or an intrinsic wave phenomena?
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This is probably a dumb question. I guess what I'm trying to ask is if radio waves travel the same speed as gamma rays, how do gamma photons carry more energy than radio photons? Do they spin faster? What other energy sources could they carry if they are moving the same speed through space?
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Quite a few of the questions given on this site mention a photon in vacuum having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at the speed of light in all frames according to special relativity.  Does a photon in vacuum have a rest frame?
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In diagrams I often see light waves depicted as little sine waves that travel through space.  And often when describing polarizers, the explainer will angle their hand to show the angle of polarization and bob it up and down in a sine wave action, apparently emulating the amplitude of the wave.  My questions is, is the amplitude of light really like this?  Where it moves up and down or side to side in space?  Or, is the sine wave relationship just an analogy?
63732
I am reading Berkeley Physics Course vol. 4 (Quantum Mechanics) , chapter 4 (photons). (1)  Section 46: book says: consider a typical photon emitted by  the source. It can be regarded as a a wave train of finite duration, spreading out in all directions in space and carrying a total energy $\hbar\omega$. If this is true, a photon emitted by a star which is few light years away, would have spread over a sphere of radius of few light years. Then it is not possible to &quot;detect&quot; that photon using a detector.  Then  why does the book say like this?  In section 47, the book gives same example of photon spreading over light years. But in this section, it says that how the people can use this as a paradox; and clarifies that paradox by saying that classical expression for &quot;energy density&quot; refers to a large number of photons, and not for single photon.  So does photon really spread in all directions?   (2)  In Section 38 book says: almost monochromatic photons can not be split into 2 photons of the same frequency which carry only a fraction of the energy of the original photon. While in section 48, it says (with reference to double-slit diffraction experiment) photon came through BOTH the slits.  Does a photon REALLY goes through both the slits? Doesn't it indicate that a single photon can be split into two photons of same frequency ?   Any help will be appreciated. Thanks
98760
This was explained to me many years ago, by a physics teacher, with the following analogy:  "If someone on the beach wants to reach someone else that is in the water, they will try to travel as much as they can on the beach and as little as possible on the water, because this way they will get there faster."  I'm paraphrasing of course, but this is as accurate as I recall it. This explanation makes no sense to me. Was he telling me the light knows where it is going? It wants to get there faster? It chooses a different direction? (No need to answer these questions, this was just me trying to understand the analogy.)  My attempts to clarify the issue were without success and many years later I still don't know.    Why does light change direction when it travels through glass?
6863
So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the "vacuum" between the atoms?
37590
Greatings!  I'm trying to understand special relativity and have one question bugging me.  In almost every book or video about the subject there is a thought experiment with moving light clock. I hope I need not elaborate on the sutup and the outcome of the experiment.  So the question is this: When a light source on the MOVING light clock emits a photon of light the path of the photon is triangular.   How this can be?   I thought since light speed is constant in every reference frame the movment of the "emmiter" can't affect the movment of the light so light should shoot right up (from the point of stationary observer) and thus move backward and up from the point of moving observer.  So you see my logic is: light speed is invariant => you can't make it move UP &amp; FORWARD only UP. i.e. you can't change it's direction once it's emited in UP direction. Why the hell light moves sideways then?  And I'm puzzeled. There is flaw in the logic but I don't see it.  Thanks for help.
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We've all heard of the inverse square law, but apparently that refers to the flux or intensity or number of photons hitting an imaginary surface area. This is not exactly what I want to ask about.  I'm asking about the energy level of an individual photon, or individual ray of light. The light could be any frequency or wavelength.  If I'm not mistaken, the amplitude of the light ray is directly related to its energy.  Consider a ray of light travelling through a vacuum. Does its energy decrease over time according to inverse square law? Maybe inverse linear? Or not at all?  This question comes from . If it's true that the energy doesn't diminish at all, then that would mean a laser beam shot into space (and never hits anything) would never lose any energy and arrive at the other side of the Universe with the same energy it started with. That's kinda hard to believe.  EDIT: It appears "energy" and "amplitude" are not synonyms for light rays. Apparently the concept of waves is tricky for light, since after all, a vacuum has no medium to propagate through in the normal wave sense. So let the question be, "Does an individual photon lose energy solely from the act of traveling through a vacuum?"