# Difference between coherent light and polarized light

• victorqedu
In summary, coherent light refers to waves that are synchronized and have a similar wavelength, while polarized light refers to waves with a specific direction of polarization. Coherent light can be polarized, but polarized light is not necessarily coherent. Additionally, polarized light can have varying wavelengths and phases.
victorqedu
What is the difference between coherent light and polarized light?

http://www.microscopyu.com/articles/polarized/polarizedlightintro.html
http://www.matter.org.uk/schools/content/interference/coherent.html

If I understand this correctly coherent light means that the waves are syncronized(in phase) and they have exactly the same wave length.

Polarized light means the waves have only one direction - the direction of the polarization.
In polarized light the waves do not have the same length and the waves are not in phase.

Coherent light is polarized, but polarized light is not coherent.

Is this correct?

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victorqedu said:
If I understand this correctly coherent light means that the waves are syncronized(in phase) and they have exactly the same wave length.

Pretty much, although I'm not sure you can get exactly the same wavelength. I think there will always be some spread, even in lasers, so you'll get decoherence after some length: this length is not infinity. According to Wikipedia:

" The most monochromatic sources are usually lasers; such high monochromaticity implies long coherence lengths (up to hundreds of meters). For example, a stabilized helium-neon laser can produce light with coherence lengths in excess of 5 m. "

So if I'm understanding this right, Star Trek lasers can't go very far to shoot ships (after some distance though, I guess the laser would reappear after all the destructive interference - recoherence?)

Besides being mostly of one wavelength, the waves being generated by the source also have to have a constant phase relation, as you say. It can't be unsteady like a lightbulb.

Also, there is the concept of spatial coherence (which to me seems very fundamentally different from the condition of being monochromatic), that if I understand it correctly, basically says your wave can't vary too much in phase if you walk along a wave envelop. This is most important for a double slit experiment (you want the light at the two slits to be mostly in phase), so my guess is that you ensure this by placing the light bulb far away from the double slit (e.g., distance stars product spatially coherent light - if something is far away it is practically a point source).

Polarized light means the waves have only one direction - the direction of the polarization.

This is mostly correct, but you can have circular or elliptical polarizations: the tip of the electric field need not be confined to a line.

In polarized light the waves do not have the same length and the waves are not in phase.

This is not true. They can be of different length and need not be in phase.

Coherent light is polarized, but polarized light is not coherent.

This is not true either. Coherent light can be unpolarized, and polarized light can be coherent.

## What is the difference between coherent light and polarized light?

Coherent light refers to light waves that are in phase with each other and have a consistent wavelength and direction. Polarized light, on the other hand, refers to light waves that are filtered so that they vibrate in a single direction.

## How is coherent light created?

Coherent light is created when all the light waves have the same frequency and are in phase with each other. This can be achieved through a process called laser amplification, where light is amplified and directed to travel in the same direction and with the same phase.

## What is the role of polarization in light?

The role of polarization in light is to filter out light waves that are not vibrating in a specific direction. This results in a more focused and consistent beam of light, which is useful in applications such as 3D glasses, LCD screens, and photography filters.

## How does polarized light affect the color of objects?

Polarized light can affect the color of objects by reducing glare and reflections. This allows us to see the true color of objects without the interference of reflected light. It also enhances the saturation and contrast of colors, making them appear more vibrant and defined.

## What are some everyday uses of coherent and polarized light?

Coherent light is used in various technological devices such as lasers, fiber optics, and holograms. Polarized light is used in sunglasses, 3D glasses, and LCD screens. It is also used in photography to reduce glare and reflections, and in microscopy to enhance contrast and detail in images.

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