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  1. J

    I was just wondering how light comes to be, from light bulbs or flash

    Since the OP's question is answered, let me use this thread for a related question. Does the electrons deep inside the material contribute to the light emission, or it is only the peripheral atoms? Let me think aloud: an inside electron created a visible light particle, but the material is...
  2. J

    Does photon have mass ?

    Since the OP's question is answered, let me use the thread for a related question. Is there anything else in the universe - detected or predicted - that has only inertial mass, but no rest mass?
  3. J

    What do they mean by Light being a wave?

    What causes the electric field to change the direction? In case of water wave, the original disturbance made in the water (say throwing a stone) pushed the neighboring water molecules away. The pushed water molecules took the least resistance path, which is upwards in the air. But due to...
  4. J

    Color and visible light in general

    Is my skin supposed to look orange, on a bright sunny day? Did you mean shape?
  5. J

    Speed of light in a moving medium

    Let's say the speed of light in a medium is c'. Assume that the medium itself is moving at a very high speed v (close to c). What is the speed of light in the moving medium if a. light and medium are moving in the same direction. b. opposite direction (can the speed be zero or negative?) c...
  6. J

    Spd. of light

    Since the OP's question is answered, I'll use this thread for a related question. If the speed of light in a different medium is c', is c' the maximum attainable speed for any object in that medium? I do not think so, but I would like to confirm it.
  7. J

    Photon hitting an electon

    Thanks for your replies. I think I used an incorrect term "double standard" here. What I meant to say was kind of "why we don't have a unified theory?" to explain everything. As you said, I think I was trying to apply the same theory to single atom and was confused. To the physics part, I...
  8. J

    Photon hitting an electon

    Feel free not to explain. I won't be offended... but there are quite a bunch a people in this forum who are very helpful.
  9. J

    Photon hitting an electon

    Let's say one photon goes through one hydrogen atom. Will the speed of the photon decrease? Can you explain what happens in each of the following cases: 1. the photon hit the electron. 2. the photon hit the nucleus.
  10. J

    Photon hitting an electon

    From the FAQ section of "why speed of photon changes in different medium". ------------- Moral of the story: the properties of a solid that we are familiar with have more to do with the "collective" behavior of a large number of atoms interacting with each other. In most cases, these do not...
  11. J

    Why Does Lightspeed = C?

    If c is derived from permiability and permittivity of free space, they are more fundamental than c. Is it right? And how do they calculate permiability and permittivity of free space?
  12. J

    Lightning in vacuum

    Can lightning travel through vacuum? Does sitting in a vaccum chamber reduce/increase/no effect the probability of being hit by lightning? If lightning can travel through vacuum, I would imagine there wouldn't be any heat or light - hence it would be just an electric shock. True?
  13. J

    Eye optics

    Is the inside of the eye ball empty space? Or it is filled with oxygen?
  14. J

    Gravity and light

    The experiment looks like a proof/observation of bending of light. If there any observable event for the bending of space? Or, is it a mathematically proved thing?
  15. J

    Gravity and light

    Few questions: 1. Is gravity always proportional to the mass of the planet/star? Is there any other factor we consider when we determine the gravity of a distant star? 2. Does light bend only if it interacts with the gravity of a huge star, or, the bend is visible with interaction huge...
  16. J

    Torch light in space

    Is it true to say, in space (or in vaccum), you wouldn't be able to see the torch light, unless you point it to your eyes?
  17. J

    Does a photon propogate faster than c ?

    No answers yet... dumb question?
  18. J

    Does a photon propogate faster than c ?

    Is the electromagnetic field strength: a) constant within the wave shown, or b) gradually (linear or non-linear) decreasing along with the amplitude and b1) zero outside the wave, or b2) zero only at infinitely far away.
  19. J

    How far the light can be shine?

    How do the scientists conclude that the particular light we received is x years old?
  20. J

    Refractive index

    (I'm still reading the QED book by Feynman...) What property of the material causes a specific refractive index for a particular medium? (in other words, from the FAQ section by ZapperZ, "So the lattice does not absorb this photon and it is re-emitted but with a very slight delay.". How is...
  21. J

    More questions on Reflection

    1. How does scientists know that the light from far distant heavenly bodies are actually from those, or some kind of reflection? 2. If a red object reflects only red frequency light, why I do not see red light from that object to the surrounding?
  22. J

    Dumb light question.

    If the reflected light is diffused due to the uneven surface of the paper, I should be seeing some random image made from some random points from the surrounding ojects, right? But, instead of that, why am I seeing the paper itself?
  23. J

    Difference between flame and light

    What's the difference between flame (due to fire) and photons?
  24. J

    Speed of light

    From the speed of light, did we derive the permeability and permittivity of space, or is it the other way? Can anyone explain permeability and permittivity of space in simpler terms? I googled those keywords, but gave me pages with lots of greek symbols, which I used to understand in the...
  25. J

    Speed of light

    Why is the speed of light limited to 3*10^8 m/s? What is blocking it from going faster than that?
  26. J

    Explaining reflection and refraction in atomic level

    I did not clearly get what was meant by interaction by the structure. Ultimately, the photon has to hit one of the atomic particles, right? I'm talking about a photon hitting an electron in an atom, not a free electron. To me, explaining things in a macro level (behavior in structure level...
  27. J

    Explaining reflection and refraction in atomic level

    https://www.physicsforums.com/showpost.php?p=899393&postcount=4 [Broken] describes why photons are slower in some medium. After reading it, I've few more questions: When a photon hits an electron, if it absorbs the photon and reemits, here's my questions: 1. How does refraction possible? The...
  28. J

    Where did the light go?

    Allright. Imagine I have a theoretical microscope that is powerful enough to see upto the subatomic particle level. If I look at an oxygen atom through that microscope, and if I bombard that nucleus with just one photon, what difference would I see? Similarly, if I bombard an electron in the...
  29. J

    Where did the light go?

    Assuming we have just one electron, at what wavelength of the electro-magnetic wave it can penetrate through the electron?
  30. J

    Where did the light go?

    Do atomic particles absorb light, or reflect them?
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