Question about visible light properties.

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Discussion Overview

The discussion revolves around the properties of visible light, specifically why we cannot see light unless it is emitted from a source or reflected by an object. Participants explore the conditions under which light becomes visible and the nature of photons in this context.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why light is not visible in transit, even when a powerful laser is used in a vacuum, suggesting that the absence of particles to reflect the light is not the sole reason.
  • Another participant asserts that light travels in a straight line, implying that this characteristic contributes to its invisibility unless it interacts with an object.
  • A different viewpoint highlights that ordinary particles can be seen in motion because they reflect or emit light, while photons themselves do not emit other photons.
  • It is noted that if a laser beam is directed at a non-reflective surface and there are no particles to scatter the light, then no photons will reach our eyes, making the light invisible.
  • Some participants express understanding of the concept, acknowledging that photons are the light itself and that visibility occurs only when photons hit the eyes.

Areas of Agreement / Disagreement

Participants generally agree on the idea that light is not visible unless it interacts with an object or reaches the observer's eyes. However, there are differing views on the implications of light traveling in straight lines and the nature of photons.

Contextual Notes

There are unresolved aspects regarding the specific conditions under which light becomes visible and the role of photons in this process. The discussion does not fully explore the implications of light behavior in various environments.

Who May Find This Useful

This discussion may be of interest to those exploring the fundamental properties of light, including students and enthusiasts in physics and optics.

JSEverex
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Why are we unable to see light except if we are looking at the light source or a source that is reflecting the light?

For example; say we set up a powerful laser but we cannot see the origin or the end point. The a vacuum is produced in the room to remove all possible particles that might reflect the laser's light. We switch the laser on but we cannot see the beam of light passing from one point to the other.

You can't really say that its because the particles are so small because if you take into account a lightsource like the sun, the light radiation and packets of quanta pretty much saturate anything in direct lines from the source (or anything reflecting the source).

So I guess the more appropriate question is why can't we quanta in transit?
 
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JSEverex said:
Why are we unable to see light except if we are looking at the light source or a source that is reflecting the light?
It's because light travels in a straight line.
 
You may be thinking of how we can see ordinary particles when they are on the move. That is becasue ordinary particles reflect or emit light i.e. photons.

Photons do not reflect or emit photons.
 
As has been pointed out, becase light goes in a straight line and if the laser is pointed at a wall (and the wall is not reflected) and there is no dust or such to scatter the light in all directons then not a single photon MEETS OUR EYE. And we see things when photons his our eyes.
 
Okay I get it. I feel a bit dumb. Photons don't emit light, they are the light, so we don't see it unless the photon hits our eyes, I get it.
 
JSEverex said:
Okay I get it. I feel a bit dumb. Photons don't emit light, they are the light, so we don't see it unless the photon hits our eyes, I get it.
Don't feel dumb. Having someone get a question answered to their satisfaction is a very rare and gratifying thing for many of us. Ask more!
 

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