Why can't light pass through to the dark side of a window?

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Discussion Overview

The discussion revolves around the phenomenon of light behavior when interacting with a window, particularly focusing on reflections and transmissions of light in different lighting conditions. Participants explore concepts related to refraction, reflection, and the perception of images through glass, as well as the implications of these effects in various scenarios.

Discussion Character

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

Main Points Raised

  • Some participants propose that when looking through a window into a darker area, one sees their reflection instead of the outside world due to the relative brightness of the two sides.
  • Others argue that the eye adapts to the total amount of light, suggesting that reflections are more noticeable when less light comes through the window.
  • It is noted that both reflected and transmitted images exist simultaneously, but the eye may prioritize the brighter image, potentially ignoring the dimmer one.
  • A participant mentions a rule of thumb regarding the percentage of light reflected at glass/air boundaries, stating it is around 4%, which is confirmed by another participant with a slight variation based on glass type.
  • There is a question about the meaning of 'n' in the formula for calculating reflection, leading to a reference to the refractive index.

Areas of Agreement / Disagreement

Participants generally agree on the principles of light reflection and transmission through glass, but there are nuances in understanding how these principles apply in different lighting conditions. Some points remain contested, particularly regarding the perception of images and the specifics of the reflection formula.

Contextual Notes

Limitations include potential variations in the percentage of light reflected based on glass type and the assumptions about eye adaptation to light levels. The discussion does not resolve the complexities of how reflections and transmissions interact under varying conditions.

Who May Find This Useful

This discussion may be of interest to individuals exploring optics, perception, and the behavior of light in different environments, particularly in relation to everyday phenomena like looking through windows.

danHa
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if I would look through a window on darker area I would see my reflection instead of the outside world . but if the other side of the window is light then the light may pass through the window does the light outside effect the window and make the refraction disappear ?.
or the light always cross both window side but our eye filter the reflection when more light is coming outside ?.
what happens if I point laser from two side of the window in difference angles on the same point would only one laser come trough the window ?.
 
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danHa said:
or the light always cross both window side but our eye filter the reflection when more light is coming outside ?.
Yes. The eye adapts to the total amount of light coming in, so you see the reflection better if there is less light coming trough the window.
 
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The reflected and transmitted images are always there. Your eye picks up the brighter image and ignores the dimmer one - it may not even be able to detect the dimmer image if the brighter one is too bright.

Sometimes the brightnesses of the two images are comparable and you can see both. You can probably see this if you live in a built up area - turn on a light inside after dark and look out at the street. You'll probably be able to see both your reflection and the outside world.

A rule of thumb (from 20 year old memory, so beware!) is that about 4% of light is reflected at each glass/air boundary. So your side needs to be quite a lot brighter than the other side for you to see a reflection.
 
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Ibix said:
A rule of thumb (from 20 year old memory, so beware!) is that about 4% of light is reflected at each glass/air boundary.
Correct. Generally 3.5% to 4%, depending on the specific type of glass.

The formula is ## \left( \frac{n-1}{n+1} \right) ^2 ##.
 
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A.T. said:
Yes. The eye adapts to the total amount of light coming in, so you see the reflection better if there is less light coming trough the window.

Redbelly98 said:
Correct. Generally 3.5% to 4%, depending on the specific type of glass.

The formula is ## \left( \frac{n-1}{n+1} \right) ^2 ##.
what n stand for?
 

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