Polarisation and electromagnetic fields

In summary, an electromagnetic wave consists of an electric field and a magnetic field oscillating perpendicularly to each other and to the direction of propagation. A polarizing filter only allows light of one particular orientation to pass through, either through the electric field or the magnetic field. It can be thought of as a pair of filters, but since they always filter both the electric and magnetic fields together, they are often considered as one filter. The convention is to think about the effect on the electric field, but it would be impossible to filter just the electric field without affecting the magnetic field.
  • #1
dt19
47
0
an electromagnetic wave contists of an electric field and a magnetic field oscillating perpendicularly to each other and to the direction of propagation. also, a polariser only let's through light of one particular orientation, so if the polariser is parallel to the direction of the oscillation of the electric field, say, does that mean that on the other side of the polariser there's no magnetic field? I'm having a little trouble getting my head around this!

ta
 
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  • #2
No, you can look at a polarizing filter from 2 points of view- either the E field OR the B field. Saying that a polarizing filter filters the E field like this:

|||||||
|||||||

is the same as saying the same filter filters the B field like this:
_____
_____
_____
_____

You always have E and B fields making up light, as one field causes the other to be formed.
 
  • #3
so a polarising filter is really a pair of filters?
 
  • #4
I suppose you could look at them like that, but since they always filter the E field and the B field together, and perpendicularly, you can just consider them to be one filter. You usually only think of what happens to the E field, just by convention. (You could just consider the B field if you wanted, but it just happens to be the E field that is usually considered.) It would be impossible to filter just the E field, say, as if there is no E field, there can't be a B field.
 

1. What is polarisation and how does it relate to electromagnetic fields?

Polarisation refers to the orientation of electromagnetic waves as they travel through space. In an electromagnetic field, the electric and magnetic fields oscillate perpendicular to each other and to the direction of wave propagation. Polarisation refers to the direction in which the electric field oscillates. This is important because it affects how the wave interacts with matter and how it can be detected.

2. How is polarisation measured?

Polarisation can be measured using a polarimeter, which is a device that can determine the direction of the electric field in an electromagnetic wave. It can also be measured using polarising filters, which only allow waves with a certain orientation of the electric field to pass through. The intensity of the transmitted wave can then be measured to determine the degree of polarisation.

3. What are some examples of polarised light?

Light from the sun or other sources is typically unpolarised, meaning that the electric field oscillates in all possible directions. However, light can become polarised when it reflects off of a smooth surface, such as water or glass. This is known as glare and can be reduced by using polarising sunglasses. Polarised light can also be produced using special materials such as polarising filters or crystals.

4. How does polarisation affect the transmission of electromagnetic waves?

Polarisation can have a significant impact on the transmission of electromagnetic waves. For example, polarising filters can be used to selectively block or allow certain orientations of light to pass through, making them useful in various applications such as photography, LCD screens, and 3D glasses. In addition, polarisation can also affect how waves interact with matter, such as in radar technology.

5. Can polarisation be changed or manipulated?

Yes, polarisation can be changed or manipulated using various techniques. For instance, polarising filters can be rotated to change the orientation of polarised light. Certain materials, such as liquid crystals, can also change the polarisation of light when an electric field is applied. This is the principle behind LCD screens. Polarisation can also be manipulated using optical elements such as wave plates or polarisers.

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