# Polarisation of reflected light

• sperryrand
In summary, the polarity of the reflected light is a function of the angle of incidence, the angle of reflectance to the eye, and the difference between v and r.
sperryrand
Hi,

I have a question regarding the projection of polarised light onto a screen, such as commonly used in 3D or VR cinemas. I'm only concerned with linearly polarised light for the moment.

I understand that when light undergoes reflection the polarity is altered.
I've attached a diagram. Light from projector is typically polarised at 45 degrees to the horizontal.
My question is, is the polarity of the reflected light a function of:
a) angle of incidence θi,
b) the angle of reflectance to the eye θv,
c) or the difference between v and r: θvr, or
d) none of the above?
Is there a simple expression, or does it depend greatly on the optical properties of the screen material? Does the Brewster angle have anything to do with this?

M

#### Attachments

• ReflectedPolarLight.png
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Hi,

Thanks. A few things are unclear to me..
a) How do I use these equations for an opaque material, where there is no transmittance or refraction? (What is the refractive index of an opaque material?)
b) These equations seem to tell me the amount of light reflected or transmitted along r - the reflection of i. But I need the ratio of the "p" component to the "s" component for light scattered in all directions.
Sorry if I am missing something obvious.
M

sperryrand said:
Hi,

I've attached a diagram. Light from projector is typically polarised at 45 degrees to the horizontal.

It's not clear if you are really interested in 3D projection or just in the phenomenon itself.
But I thought that in 3D projection they use circular polarization.

Hi,

I'm interested in the degradation of stereo contrast (i.e. increase in cross-talk) caused by high angles of incidence and reflection.
Yes, in some theatres it is circular, but in others linear. Here, I have a linear system.
M

## 1. What is polarisation of reflected light?

Polarisation of reflected light refers to the orientation of the electric field in a light wave that is reflected off a surface. When light waves bounce off a surface, they can become polarised in a specific direction, which affects how the light is perceived by our eyes.

## 2. How does polarisation occur in reflected light?

Polarisation occurs when unpolarised light, which has electric fields oscillating in all directions, hits a surface and the reflected light is filtered to only allow electric fields oscillating in a specific direction to pass through. This results in the light becoming polarised in that direction.

## 3. What are some examples of polarisation in everyday life?

Polarisation can be observed in various aspects of everyday life, such as the glare on a car windshield or the reflection of light off of a body of water. It is also used in polarised sunglasses to reduce glare and in 3D movie technology to create depth perception.

## 4. How does polarisation affect the appearance of objects?

When light is polarised, it can change how objects appear to our eyes. For example, polarised light can make shiny or reflective surfaces appear darker or more muted, while non-reflective surfaces may appear to have more contrast and detail.

## 5. Can polarisation of reflected light be manipulated?

Yes, the polarisation of reflected light can be manipulated using polarising filters, which are materials that only allow light waves of a specific orientation to pass through. They can be used to control the amount and direction of polarisation in reflected light, making them useful in photography and other scientific applications.

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