Lightspeed fast, then slowed, then fast again.

  • Context: Undergrad 
  • Thread starter Thread starter mapper
  • Start date Start date
  • Tags Tags
    Lightspeed
Click For Summary

Discussion Overview

The discussion centers around the behavior of light as it passes through different media, specifically addressing the apparent slowdown of light in materials like water and glass, and its return to the speed of light in a vacuum. Participants explore the implications of this behavior on the conservation of energy, referencing Newton's laws.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions how light can return to its speed after passing through a medium, suggesting a potential contradiction with the conservation of energy.
  • Another participant asserts that light always moves at the speed of light "c," explaining that the apparent slowdown is due to matter absorbing and reemitting light.
  • Further contributions emphasize that energy is conserved throughout this process, with one participant reiterating that light never stops moving at "c" and that the energy remains consistent.

Areas of Agreement / Disagreement

Participants express differing views on the nature of light's speed in various media and the implications for energy conservation, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

The discussion does not resolve the underlying assumptions about the interaction of light with matter and the definitions of speed in different contexts.

mapper
Messages
123
Reaction score
0
I was reading material on light speed and have a question about something I thought may contradict Newtons law of conservation of energy.

Light slows down as it passes through water, glass etc.. right? But when it reaches the other side it continues at light speed. Where is it getting its energy/power supply to continue back at its normal speed? Whats happening here? :eek:
 
Science news on Phys.org
It ALWAYS MOVES AT "c"...It's just that matter absorbs it & reemits it and that's why the apparent "slowdown" due to presence of matter...

Daniel.

P.S.Energy is conserved.
 
ahh, thanks.
 
it never stops moving at "c" :D just the matter makes it slow down, but the nergy is used the same :D
 

Similar threads

Undergrad Achieving the speed of light at the end of a whip
  • · Replies 15 ·
Replies
15
Views
6K
Graduate Why light slows in transparent media
  • · Replies 4 ·
Replies
4
Views
10K
Graduate The microscopic expl. of how light is slowed in materials
  • · Replies 2 ·
Replies
2
Views
11K
High School Where am I wrong in this travelling faster than light Idea I've had?
  • · Replies 17 ·
Replies
17
Views
4K
Undergrad Energy and reference frames
  • · Replies 87 ·
3
Replies
87
Views
6K
Graduate Speed of light and bending time
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Single-slit diffraction experiment and the conservation of energy
  • · Replies 20 ·
Replies
20
Views
3K
High School Why does it require an infinite amount of energy to reach the speed of light?
  • · Replies 130 ·
5
Replies
130
Views
17K
Undergrad Why does the core collapse happen so fast in a supernova?
  • · Replies 3 ·
Replies
3
Views
4K
Undergrad Understanding Light Slowing in a Medium
  • · Replies 3 ·
Replies
3
Views
4K