If light hits a mirror and then switches direction

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Discussion Overview

The discussion centers around the behavior of light when it interacts with mirrors, specifically addressing whether light slows down upon hitting a mirror and the nature of reflection versus refraction. Participants explore concepts related to the speed of light, reflection, and the mechanics of light interacting with different types of mirrors.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that light must travel slower than the speed of light when it hits a mirror at a 90-degree angle.
  • Another participant questions this assertion, asking for clarification on why light would slow down.
  • It is proposed that light reflects from a mirror by being absorbed and re-emitted, rather than stopping and changing direction.
  • A participant introduces the concept of refraction, noting that it involves a change in phase velocity when light is absorbed in a medium.
  • There is a discussion about whether the angles of reflection for light are similar to those of solid objects bouncing off walls, raising questions about the consistency of reflection for light.
  • A later reply points out that light hitting a conventional rear-surface silvered mirror travels slower than its normal speed in air while in the glass, contrasting this with front-surface silvered mirrors where light reflects directly back into the air.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of light when reflecting off mirrors, particularly regarding the speed of light and the mechanics of reflection versus absorption. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Participants reference different types of mirrors and their effects on light, indicating that assumptions about the behavior of light may depend on the specific context of the mirror type used.

seerskater
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if light hits a mirror and then switches direction...

if light hits a mirror at a 90 degree angle, wouldn't it HAVE to travel slower than the speed of light when it hit the mirror?
 
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No. Why?
 


When light reflects from a mirror, it is absorbed by the mirror and re-emited. It does not "stop" and change direction.
 


HallsofIvy said:
When light reflects from a mirror, it is absorbed by the mirror and re-emited. It does not "stop" and change direction.

I meant more what hallsofivy guessed. That is interesting though. Would the angles of reflection the same for a solid object bouncing off a wall? it seems odd that light's angle of reflection wouldn't be jumbled around somehow while it was absorbed by the mirror.
 


Just a niggle, here. If light hits a conventional rear-surface silvered mirror it will travel slower than its normal speed in air when it hits the glass, until it is reflected by the silvering and re-exits the glass and re-enters air. This is not situation with a front-surface silvered mirror like those used in telescopes or the larger flat mirrors that are used to allow optometrists/ophthalmologists to test your visual acuity in small exam rooms. In such cases, the light is reflected right back into the air and does not have to traverse any glass.
 

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