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# Physics/Passing light beams into water molecules....

Question
QUESTION: Hello,

When beams of light pass through a glass of water or in the air, in fact , those beams of light pass into the molecules
of water or into the molecules of the air: And the question is how the beams of light come into the body[the air or water molecules] and come out from those bodies?

Thanks,

ANSWER: I'm a little unsure what you mean by your question.  Light is an electromagnetic wave, it obeys a wave equation.  The wave equation is slightly adjusted by the presence of molecules (which can alter the permeability of space to electric and magnetic fields, slightly adjusting the parameters of the equation from those in empty space), which can cause refraction and other effects.  In the case of the main effect, refraction, the light obeys Snell's law of refraction as a consequence of obeying its wave equation.  Do you have a more specific question about light "coming into a body?"

---------- FOLLOW-UP ----------

when we radiate a beam of light,for example,from a very tiny hole into a glass of
water or a window glass that covered by a black covering but a tiny hole left uncovering on them,exactly against in front of that aperture,that beam of light
should passes through the glass molecules and the inner of those molecules,
when it meets the glass,as the particle/photon behavior of beam light,to come out from the other side of that glass(of water or window);the beam really passes through into the molecules and the refraction does not occur here.And,could I conclude that ;
A BEAM OF LIGHT CAN PASSES THROUGH A BODY(A MOLECULE)THAT IS NOT TRANSPARENT?

Thanks,

First, refraction does occur.  The light slows down according to the index of refraction of the glass.  Second, visible light wavelengths are huge compared to the size of the atoms they're passing through.  The atoms are more like tiny bits on huge ocean waves.  So it's not that it passes through something that is not transparent.  The light interacts with it, causing it to polarize, but the light is re-emitted in a direction that favors the momentum (yes, light also has momentum) in the direction of its travel.

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#### Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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