Judging distance of a light source

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Discussion Overview

The discussion revolves around methods to judge the distance of a light source by analyzing its characteristics, focusing on the possibility of creating a device similar to a laser range finder that relies solely on received light without emitting any signals. The scope includes theoretical considerations and practical applications related to light properties and distance measurement techniques.

Discussion Character

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

Main Points Raised

  • Some participants suggest that knowing the power of the light source could allow for distance estimation, but note that environmental conditions like dust and humidity can significantly affect results.
  • One participant proposes that the angle of divergence of the light could indicate the nature of the source, implying it might be spherical.
  • Another participant mentions that light energy attenuates in air or other media, suggesting that measuring energy loss could help determine path length.
  • A participant raises the idea of using parallax for distance measurement, referencing how single-lens reflex cameras achieve this.
  • One participant introduces the concept of cosmic distances, mentioning type 1a supernovae and cosmic microwave background radiation as references for measuring vast distances.
  • A later reply clarifies the interest in short distances, specifically between 1-1000 meters, and expresses a desire to explore how cameras determine distances when focusing.

Areas of Agreement / Disagreement

Participants express a range of ideas and methods for estimating distance, but there is no consensus on a definitive approach or solution. Multiple competing views and techniques are presented, indicating an unresolved discussion.

Contextual Notes

The discussion includes various assumptions about light properties, environmental influences, and measurement techniques that remain unaddressed or unresolved.

Who May Find This Useful

This discussion may be of interest to those exploring optical measurement techniques, distance estimation methods, and the properties of light in different media.

NPacific
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Is there a way to judge the distance of a light source, or from where it was last reflected, by analyzing the characteristics of the light? Are there any properties of light that change, or better yet, consistently change over distance? I'm trying to figure out if somehow there would be a way to make a laser range finder type device, but by only analyzing the light received, and not having to emit anything.

Thank you for your help.
 
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If you know something about the power of the light source, you may judge the distance, otherwise, it is impossible. Even though, the result may be affected a lot by the environment conditions : dust, humidity etc..
 
Couldn't the angle of divergence tell you something amusing that it is a spherical source?
 
When the light propagation in air or some other medium, the energy will be attenuating, due to the absorbs. So, you can judging the distance of the path length by measuring the energy loss.
Usually, the light beam is not the perfect plane wave, the beam width also
changes with the distance.
 
NPacific said:
Is there a way to judge the distance of a light source, or from where it was last reflected, by analyzing the characteristics of the light? Are there any properties of light that change, or better yet, consistently change over distance? I'm trying to figure out if somehow there would be a way to make a laser range finder type device, but by only analyzing the light received, and not having to emit anything.

Thank you for your help.
What if you eimply triangluated the distance using parallax? Look at how a single-lens reflex camera can tell the distance to an object.
 
Are you interested in a few miles or cosmic distances? If the latter, try ready about type 1a supernova (standard brilliance references) and analyzing cosmic microwave background radiation...over cosmic distances light is red shifted due to an expanding universe...
 
I'm interested in short distances, from about 1-1000 meters. Thank you for your guidance so far, I'm looking into the way cameras tell distances when focusing like Dave pointed out.
 

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