Does Glass Affect the Speed of Light's Travel from A to B?

Click For Summary

Discussion Overview

The discussion centers on whether the presence of glass affects the speed of light traveling from point A to point B. Participants explore the implications of light's behavior in different media, particularly focusing on concepts like the index of refraction and the effects of refraction on speed and distance. The scope includes theoretical considerations and conceptual clarifications regarding light propagation in materials.

Discussion Character

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

Main Points Raised

  • One participant questions whether the total time for light to travel from A to B is affected by the presence of glass, suggesting that if light slows down in glass, the answer would be yes, but notes the complexity of the index of refraction.
  • Another participant explains that the actual time taken is influenced by both the speed of light and the distance traveled, indicating that the effects of slowing down in higher-index materials and bending towards the normal could potentially cancel each other out, depending on various factors like the material's index of refraction and angle of incidence.
  • A participant challenges the assertion that light slows down in higher-index materials, mentioning that they have heard conflicting viewpoints and referencing a knowledgeable source who claims that glass affects the phase of light rather than its speed.
  • In response, another participant asserts that light does indeed slow down in higher refractive index materials, explaining that the refractive index is a ratio comparing materials and that light interacts with the medium, causing delays that affect average velocity.
  • This participant also introduces the idea that commercial integrated circuits can digitally control the speed of light, linking refractive index to molecular structure and dipole alignments.

Areas of Agreement / Disagreement

Participants express differing views on whether light truly slows down in glass or if it is merely a phase effect. There is no consensus on the nature of light's interaction with glass and how it affects travel time.

Contextual Notes

The discussion highlights the complexity of light behavior in different media, with various assumptions about the nature of refractive index and its implications for speed and distance remaining unresolved.

ralqs
Messages
97
Reaction score
1
If a light travels from A to B and there's a plane of glass in between the two points, will the total time it takes to make the journey be different than if there was no glass? If light slows down in glass, then I guess the answer would be yes, but I've read that the index of refraction is more subtle than that.
 
Science news on Phys.org
actual time taken between two static space points will be a product of the speed and distance traveled. The refraction of light by a dielectric material will effect both speed and distance. The light will slow down in higher-index materials, but it will also bend towards the normal which decrease the distance it travels through the layer. With the speed slower but the distance shorter, both effects could cancel out and you could end up with the same travel time. I think it will depend on the specifics of the material's index refraction, thickness, angle of incidence, etc. to determine which effect dominates.
 
chrisbaird said:
The light will slow down in higher-index materials..
Is that a fact? I've heard contradicting points on this. Someone quite knowledgeable about physics told me that the glass just affects the phase of the light in a way that makes it appear as if the light slowed down in glass.
 
ralqs said:
Is that a fact? I've heard contradicting points on this. Someone quite knowledgeable about physics told me that the glass just affects the phase of the light in a way that makes it appear as if the light slowed down in glass.

Yes that's a fact. Actually refractive index is just comparison ratio between materials where n of vacuum is taken 1 as reference. Light doesn't just pass by from a medium, it interacts with it. Material having higher refractive index interacts with light more than lower index one. Each interaction is a delay thus affects the average velocity.

Light travels at different velocities in different mediums. Even more there are commercial IC's that offers features such as digitally controlling the speed of light in a chip. Refraction index is related to molecule's geometrical structure and dipole alignments.
 

Similar threads

Undergrad Why is Cherenkov radiation blue? And what about refractive index?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Outer layer refractive index - total internal refection on waveguide
  • · Replies 2 ·
Replies
2
Views
2K
High School Refractive Index: Light Speed & Distance Perception
  • · Replies 14 ·
Replies
14
Views
4K
Refraction of light when traveling from air to glass
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Speed of light of different wavelengths in medium
  • · Replies 8 ·
Replies
8
Views
10K
Undergrad How does optical density relate to mass density and refractive index?
  • · Replies 7 ·
Replies
7
Views
20K
Undergrad How Does Polarization by Reflection Determine the Refractive Index of Glass?
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Dependence of index of refraction on frequency
  • · Replies 15 ·
Replies
15
Views
4K
Graduate Does this mean the speed of x ray faster than light in vaccum
  • · Replies 9 ·
Replies
9
Views
12K
Undergrad Refractive index of a medium in relativistic motion
  • · Replies 14 ·
Replies
14
Views
4K