Polaroid filters

Polaroid filters

1. Plane polarisation is the method of allowing only waves orientated in the same direction - only allowing vibrations in one plane.

2. Only transverse waves can be plane polarised because their vibration is perpendicular to the direction of energy travel - you can therefore have this vibration at different orientations.

3. Longitudinal waves cannot be plane polarised because the direction of vibration and direction of propagation are the same.Acoustic waves (sound waves) in a gas or liquid do not have polarisation - but all of the electromagnetic waves do.

4. Polarisation is the orientation of vibration perpendicular to the direction of energy travel. It can be measured with a polarimeter.

5. When electromagnetic waves travel through space they do so at all orientations. The direction of energy movement will be at some angle to the path it is travelling; this is what is called polarisation.

6. Polarisation by reflection: Light reflecting off water (or any other shiny but non-metallic surface) will be partially polarised; this is because the component of the light which is perpendicular to the surface is inverted by being reflected, and interferes with itself destructively. See polaroid sunglasses.

7. The most common method of polarization involves the use of a Polaroid filter. Polaroid filters are made of a special material that is capable of blocking one of the two planes of vibration of an electromagnetic wave.

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