OPTICS and GRAVITY

Discussion in 'Astronomy, Exobiology, & Cosmology' started by hansda, Sep 9, 2012.

  1. hansda Valued Senior Member

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    Are they dependant or independent?


    Considering the cases of Reflection and Refraction; Optics and Gravity are independant.


    Considering the case of Gravitational lensing; Optics is dependant on Gravity.


    Is it that at weak gravitational field, Optics and Gravity are independant?


    Is it that at strong gravitational field, Optics is dependent on Gravity?


    Reflection and Refraction of Light also can happen at strong gravitational field.


    Are Reflection and Refraction of Light at strong gravitational field dependant or independant of Gravity?
     
    Last edited: Sep 9, 2012
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  3. tashja Registered Senior Member

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    By ''Optics'' you mean the electromagnetic field, right?

    I think there is some relationship between the gravitational field and the electromagnetic field, yes.
     
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  5. James R Just this guy, you know? Staff Member

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    Light is bent by gravity. Is that all you're asking about?
     
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  7. hansda Valued Senior Member

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    This is gravitational lensing as per GR, which can be observed at a strong gravitational field.


    My question is that, in a strong gravitational field where gravitational lensing can be observed; does gravity affect Reflection or Refraction of Light?
     
  8. hansda Valued Senior Member

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    Light is also considered as electromagnetic wave.

    Are the Laws of Reflection and Refraction depended upon Gravity?
     
  9. tashja Registered Senior Member

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    Reflection and refraction follow the laws of quantum mechanics. I don't know the role gravity plays at that level. I just don't know.
     
  10. Rhaedas Valued Senior Member

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    The actual angle of incidence for any given point shouldn't change, although the surface itself would, as well as the path of the light. But how much it is measurable would vary based on the gravity strength.
     
  11. OnlyMe Valued Senior Member

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    It sometimes amazes me just how simply something can be put!

    The way I interpret the quoted post is; Reflection and refraction, as we experience them, is explained well in terms of quantum mechanics... Quantum mechanics at the scales that are involved does not include gravity.

    That said, using a mirror as an example the actual reflection occurs in a way consistent with quantum mechanics.., but the mirror itself, a macroscopic object from a quantum mechanical point of view, can and would be affected by any gravitational field it is subjected to... The shape of the mirror and it's surface would be affected by gravity and the shape change may affect the way light is reflected.

    Merging and reconciling quantum mechanics and general relativity, is something that can only be described as a work still in progress. But in the case Hansda has raised both do logically have an influence on how light is reflected or refracted.

    We just don't know yet how they can each be explained, QM and GR, in a uninfield theoretical framework.
     
  12. hansda Valued Senior Member

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    If a mirror is kept in the path of Light where gravitational lensing is happening, how the Reflected Light would travel? In a straight Line or in a curved Line?


    Do you think the Law of Reflection depends on gravity strength or GR?

    I dont think so. Trajectory of Light may be curved but The Law of Reflection should not depend on gravity strength.
     
  13. OnlyMe Valued Senior Member

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    Hansda, I think what Rhaedas was saying is that reflection occurring at any point on a mirror's surface is accurately described by quantum mechanics, which does not include or involve the curvature of space, at least as far as that point on the mirror is involved.

    However, the mirror is big and the shape of the mirror itself can be changed by the curvature of space, so different points on the mirror's surface would reflect light at different angles, when the mirror is in a strong gravitational field, than when it is far from a strong field.

    But, light always follows the curvature of space, even when that curvature is far too small for us to measure. The only place where there is NO curvature is where there is no gravitational filed at all. And at least as we currently understand it, there is nowhere where there is no gravitational field.

    For a single point on a mirror, curvature is as insignificant as it can ever get. The point itself does not experience any curvature. Still as the photon approaches the mirror and after it reflects from the point on the mirror, it always follows the curvature of space... Again even when, in a weak field, we cannot measure that curvature.
     
  14. hansda Valued Senior Member

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    Light can not pass through the mirror and gets reflected by the mirror.


    Gravity can pass through the mirror and can affect the mirror but the Law of Reflection remains unaffected by gravity.


    So, at the point of reflection gravity and light are separated.
     
  15. Rhaedas Valued Senior Member

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    Right. Picture a large flat mirror in zero gravity. The angle of reflection would be a certain exact angle with the light path straight and out.

    Now if we increase gravity at a point in space centered behind the mirror, both the light's path in and out would be affected, as well as the actual surface, so the path of light would begin to bow as the gravity went up, very minutely at first, but the actual point of reflection will behave the same way at it did in zero g, as it is a single point of interaction with the surface.

    I think maybe what you're pointing out in your last post is that this would be true in a perfect situation, but in reality the light has to travel through the glass, strike, the mirrored surface, etc, and yes, in that case, things change, because the mirror's shape and volume changes. But the point of interaction is immune to gravity, as it is a point, only its relation to other points.
     
  16. hansda Valued Senior Member

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    A mirror does not cause gravitational lensing. A mirror can only reflect Light.
     
  17. hansda Valued Senior Member

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    So, Law of Reflection is unaffected by gravity whatever may its gravity strength.
     
  18. Rhaedas Valued Senior Member

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    Only the path before and after, and keep in mind that the shape of the reflector as well, so while each point doesn't change, the overall reflection of all the light paths will.
     
  19. hansda Valued Senior Member

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    Instead of mirror if a prism is placed in the path of Light, where 'gravitational lensing' is happening; what will be the trajectory of light through the prism?

    Certainly the path of light will deviate from its earlier path where it was following 'curvature of spacetime', though the 'curvature of spacetime' through the prism will remain unaffected.

    'Laws of refraction' also will remain unaffected by gravity or GR.
     
  20. Rhaedas Valued Senior Member

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    I would say that it would act the same through the prism as with no gravity. The prism volume is within spacetime, as is anything else, so the path of light inside would be affected just as if it was outside. As the mirror before bent according to the amount of gravity, so would the prism, but to see the affect, you'd have to have an extreme curvature, or a very large prism.
     
  21. hansda Valued Senior Member

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    So, the effect of prism or the Laws of Refraction are unaffected by gravity or GR.


    Here through the prism 'curvature of spacetime' and 'path of light' will be different.


    Here material of prism is also important.
     
  22. Rhaedas Valued Senior Member

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    They are one and the same. A prism bends light through the refraction of incoming light on one side and outgoing light on the other.

    Internally, assuming the same material, the path of light will remain straight, relative to spacetime. So if spacetime is curved, the light will follow.

    Not for the question you're asking.
     
  23. hansda Valued Senior Member

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    right.



    1) In gravitational lensing, path of light follows 'curvature of spacetime'.

    2) Now a prism is placed in this path of light.

    3) Through the prism light will be refracted but spacetime will remain unaffected.

    So through prism, 'curvature of spacetime' and 'path of light' will be different.



    I mean refraction of light depends upon material of prism.
     

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