What is the nature of refraction ?

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Discussion Overview

The discussion revolves around the nature of refraction, particularly focusing on how light behaves when transitioning between different media. Participants explore both the macroscopic and microscopic explanations of this phenomenon, including the roles of electromagnetic waves, particle interactions, and conservation laws.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the bending of light is due to interactions between photons and atoms in the medium, suggesting that this occurs at a microscopic level.
  • Others argue that when light changes medium, its speed changes according to Snell's law, which governs the bending of light based on the density of the substances involved.
  • A participant mentions that conservation of momentum can explain the bending of light when viewed as particles, while another suggests a wave perspective using an experimental analogy with oil and water.
  • One participant expresses skepticism about the explanations provided in electrodynamics, arguing that the slowing of light is a macroscopic phenomenon that does not necessarily reflect the behavior of individual photons at the microscopic level.
  • Another participant raises a question about why different colors of light (e.g., red and blue photons) refract at different angles when passing through glass, indicating a complexity in the interaction that is not fully understood.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the root cause of refraction, with multiple competing views and uncertainties remaining regarding the microscopic versus macroscopic explanations of the phenomenon.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the nature of light, the definitions of speed in different contexts, and the unresolved details of the interactions at the microscopic level.

blenx
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Take Electromagntic wave for example , when light pass from vacuum to one medium , how does the atoms of the medium bend the light towards a certain direction at the microscopic level ?
 
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As far as I know, when light changes from medium to another medium (i.e. a difference in the density of the substance) the light will change its speed as well. At the time it changes the speed it will also bend according to the Snell's law. So my advice if you really want to know the nature of Snell's law is to read an article about it.
 
Last edited:
blenx said:
Take Electromagntic wave for example , when light pass from vacuum to one medium , how does the atoms of the medium bend the light towards a certain direction at the microscopic level ?


By reducing the speed of propagation from c_0 to c_0/n. Momentum is conserved, so the direction of propagation changes.
 
If you think of light in terms of particles, then it's because of conservation of momentum.

If you don't want to use conservation of momentum, you can think of light in terms of a wave. You can try an experiment - Put thin oil and water into a container and separate them by a very thin plastic film. If you make a wave in one fluid you will see the wave 'change direction' slightly when it hits the other fluid, because of speed changes.
 
 I have learned electrodynamics , whose explanation of refraction I think is quite phenomenological. Because it have not touched on the microscopic details when light enter the medium .

 It is certain that the bending of light must be due to the interaction between photon and atoms , but I don't think the speed of photon will be slowed down after the interaction at the microscopic level . The slowdown of a light wave is a macroscopic phenomenon which invlove with lots of microscopic details . In this sense , conservation of momentum cannot ensure the photon will turn to a certain direction after interaction . It's possible for the phton turn to another direction and the momentum conservation law also holds .

 So, what is the root cause of refraction ?
 
I have wondered this my self , and most people say the speed changes , but we all know that light always travels at c , so the speed is not changing , it is just the time lag from it interacting with the electrons and other stuff it is pretty complicated but anyways , when white light hits the glass why do the red photons take a different angle then the blue photons .
 

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