Light -- why does it bend/refract?

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In summary, light bends in a medium due to the change in its speed as it enters a material with a higher refractive index. This is a result of light acting as a wave and the change in speed is caused by the interaction of light with atoms in the material. However, the complete explanation is complex and depends on the type of material.
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NUCLIDES
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why exactly does light bend in a medium??
 
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There is this really nifty facility on the Internet called "Google Search". You would do well to learn how to use it. You can ask such questions directly and get good answers. When I Google that exact phrase, I got 20,000,000 hits and the ones on the first page of the search results were quite good.
 
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I mean on an atomic scale what exactly happens?
 
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NUCLIDES said:
I mean on an atomic scale what exactly happens?

There is no atomic scale. Photons are not atoms. It's more complicated than that. I suggest that you do some research on your own and come back if you have amore targeted question.

The short answer is that light has an energy that is the equivalent of mass and that "mass" is attracted by massive objects.

EDIT: OOPS ... I see that your original question wasn't why light bends around massive objects but why it bends when entering, say, glass. Google "diffraction".
 
  • #5
phinds said:
There is no atomic scale. Photons are not atoms. It's more complicated than that. I suggest that you do some research on your own and come back if you have amore targeted question.

The short answer is that light has an energy that is the equivalent of mass and that "mass" is attracted by massive objects.

EDIT: OOPS ... I see that your original question wasn't why light bends around massive objects but why it bends when entering, say, glass. Google "diffraction".

Firstly I am speeaking about refraction not diffraction. And next I am asking what triggers the light to bend, there seems to be no exact answer to this. Like we can explain reflection by considering light as particles and elastic collisions , diffraction by considering light as waves etc.
 
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NUCLIDES said:
Firstly I am speeaking about refraction not diffraction.

OOPS. My bad. I have very mild dyslexia and I make this kind of bone-headed word substitution sometimes. I once wrote a whole post here using the word proton when I meant photon. Folks thought I was nuts :smile:
 
  • #8
NUCLIDES said:
why exactly does light bend in a medium??
See http://www.gcsescience.com/pwav42.htm It is about water waves but the same is true for light.

http://www.gcsescience.com/Refraction-Water-Waves.gif [Broken]

The parallel lines represent the wave-fronts (places of equal phase). The distance between them is equal to the wavelength. In the material of higher refractive index, the speed of the wave is less than in the low-index material. You see the wave-front changing shape and bend when it reaches the interface , as the part in the hight-index medium slows down.

It is an other question why is the speed of light less in a medium than in vacuum. You can explane it with the interaction of light with the atoms.

ehild
 
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  • #9
ehild said:
It is an other question why is the speed of light less in a medium than in vacuum. You can explane it with the interaction of light with the atoms.

The complete answer in terms of quantum physics of materials is rather complex, and depends on the kind of material. You might get an idea of it from this FAQ post:

https://www.physicsforums.com/showthread.php?t=511177 [Broken]
 
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1. Why does light bend when it passes through different materials?

Light bends or refracts because it changes speed when it travels from one medium to another. The speed of light is different in different materials, and this change in speed causes the light to bend as it passes through the material.

2. What is the role of the angle of incidence in light refraction?

The angle of incidence is the angle at which light hits the surface of a material. When light passes from one medium to another, the angle of incidence determines the amount of bending that will occur. A larger angle of incidence results in a larger amount of refraction.

3. Why do different materials refract light at different angles?

The refractive index of a material is what determines how much light will bend when it passes through the material. This index is dependent on the physical properties of the material, such as its density and composition, which vary between materials and thus result in different angles of refraction.

4. How does light refraction affect the appearance of objects?

When light enters a material at an angle, it bends and changes direction. This can cause objects to appear distorted or even invisible if the light is bent away from the viewer's line of sight. This is why objects in water may appear closer than they actually are.

5. Can light refract in a vacuum?

No, light cannot refract in a vacuum because there are no particles or materials for it to pass through and change speed. Light only bends when it passes from one medium to another, such as air to water or glass.

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