Understanding Light in a Sheet of Glass

In summary: This is why you'll sometimes see a thin line of light on the side of a drinking glass that's been turned so that the light from a nearby candle is shining on it. The thin line of light is the result of a minimum in the reflective amplitude as the thickness of the glass increases from the point of the candle to the point of the glass where the light from the candle is being reflected. Also, understand that this sheet of glass (which I assume is very close to the projector) is intercepting the light when it is much, much stronger.
  • #1
niksoley
2
0
I need help to understand what is happening when I project a image in a sheet of glass.
Imagine this picture, a projector as the light source projecting a image in a sheet of glass:
1: I have high transmission. (the light that pass away the sheet of glass)
2: Low absortion
3: A so so reflection (part of the light is reflected at my wall)
4: Low Scattering
5: Refraction ?

The light that pass the sheet of glass make a image on the other side of the projector(transmission), but the image appears too in the sheet of glass. Is the image that appear in the sheet of glass a absortion or a refraction?
 

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  • #2
Neither. It's a reflection, about 4% from each side.
 
  • #3
Antiphon said:
It's a reflection

Reflection won't cause an image to form at the reflecting surface. What you see is impurities in the glass, dust on the surface etc. acting as a rather nebulous projector screen. A bit like a layer of very thin smoke.
 
  • #4
AJ Bentley said:
Reflection won't cause an image to form at the reflecting surface. What you see is impurities in the glass, dust on the surface etc. acting as a rather nebulous projector screen. A bit like a layer of very thin smoke.

I agree with you in part. I think it isn't only impurities, probably its a propertie of the arrange of the electrons of the glass. If its only impurities or electrons arrangement, the image is form from the fluorescent absorption, right?
 
  • #5
niksoley said:
I agree with you in part. I think it isn't only impurities, probably its a propertie of the arrange of the electrons of the glass. If its only impurities or electrons arrangement, the image is form from the fluorescent absorption, right?

Doubtful - I would guess it's all dust on the glass or surface imperfections resulting in scattering.

Fluorescence would not show the same color as the image being projected - it would absorb the energy and emit it at some other wavelength.


Also, understand that this sheet of glass (which I assume is very close to the projector) is intercepting the light when it is much, much stronger.

For example, our movie projector projects an image which appears very, very bright when spread out to shine on a screen that is, say, somewhere in the neighborhood of 30 feet long by 15 feet tall, but the glass that separates the projector from the theater intercepts the light right next to the projector, when the image is only 4 inches across. So you're looking at light that is ~8000 times brighter where the glass is than when it hits the screen (which is really, really bright, which is why any diffuse scattering from surface imperfections and dust is so bright, and why you may see light scattering after one or more internal reflections inside the glass).
 
  • #6
Partial reflection is a QM effect that varies with the ratio of the glass thickness to the wavelength of the light. The reflective variance will actually oscillate between minimums and maximums as the thickness of the glass is continually increased.
 

1. How does light pass through a sheet of glass?

Light travels through a sheet of glass by being absorbed and re-emitted by the atoms in the glass. As the light passes through the glass, it is slowed down and refracted due to the difference in density between the air and the glass. This is what allows us to see through the glass.

2. Why does light appear to bend when passing through a sheet of glass?

The bending of light, also known as refraction, occurs because the speed of light changes as it passes from one medium (such as air) to another (such as glass). This change in speed causes the light to change direction, resulting in the appearance of bending.

3. What factors affect the amount of light that passes through a sheet of glass?

The amount of light that passes through a sheet of glass can be affected by several factors, including the thickness of the glass, the type of glass (such as clear or tinted), and the angle at which the light passes through the glass. The refractive index of the glass also plays a role in determining how much light is transmitted.

4. How does the color of light affect how it passes through a sheet of glass?

The color of light can affect how it passes through a sheet of glass because different colors of light have different wavelengths. This means that they are refracted at different angles as they pass through the glass, resulting in different amounts of light being transmitted. For example, red light has a longer wavelength than blue light, so it is less likely to be refracted and more likely to be transmitted through the glass.

5. Can light be reflected off of a sheet of glass?

Yes, light can be reflected off of a sheet of glass. This is because glass is a smooth and shiny surface, making it a good reflector. The angle at which the light hits the glass will determine the angle at which it is reflected. This is why you can see your reflection in a sheet of glass.

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