Ordinary light and monochromatic light

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Discussion Overview

The discussion revolves around the definitions and characteristics of ordinary light and monochromatic light, exploring their differences, properties, and implications in various contexts such as optics and wave theory.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants define ordinary light as consisting of rays of different wavelengths vibrating in all possible planes, while monochromatic light consists of rays of a single wavelength vibrating in different planes.
  • There is a distinction made between unpolarized and polarized light, with some participants noting that ordinary light is polychromatic and unpolarized, whereas monochromatic light can be either polarized or unpolarized.
  • Participants discuss the composition of light, questioning whether rays and waves are the same and whether light is made up of rays or waves.
  • Some participants assert that light can be described as photons, waves, or disturbances of fields, indicating that different models can be used to understand light behavior.
  • There is a discussion about the direction of propagation of light and whether it is the same as the direction of propagation of the waves that make up light.
  • Participants explore the implications of light being emitted in different directions and how this relates to the perception of color, particularly in relation to white light and the use of prisms.
  • One participant suggests rephrasing the definition of ordinary light to include "electromagnetic waves" instead of "rays," while questioning the accuracy of describing vibrations in all possible planes.

Areas of Agreement / Disagreement

Participants express various viewpoints on the definitions and properties of ordinary and monochromatic light, with no clear consensus reached on several aspects, including the nature of rays versus waves and the implications of light propagation directions.

Contextual Notes

Some statements reflect assumptions about the nature of light and its behavior, which may not be universally accepted. The discussion includes unresolved questions about the definitions and characteristics of light, as well as the implications of different models used to describe it.

  • #31
For each SINGLE ray/photon/wave - whatever we decide to call it - fields vibrate in such a way that B is perpendicular to E and both are perpendicular to K. But if we take collimated light (that is, all have the same K) it doesn't mean B of one photon is parallel to B of another photon - they can be at any angle. We can filter the light to separate all photons of parallel Bs (this will also make their Es parallel) - that will be what we call polarized light.
 
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  • #32
Can you post the picture of electromagnetic wave vibrations in case of light? I tried to find it but failed.
 
  • #33
What is wrong with the one you posted? It looks perfectly OK to me.
 
  • #34
Borek said:
What is wrong with the one you posted? It looks perfectly OK to me.
But these vibrations aren't in all possible planes perpendicular the direction of wave propagation (vector K)
 
  • #35
gracy said:
But these vibrations aren't in all possible planes perpendicular the direction of wave propagation (vector K)

Well, you liked the post where I have explained what is going on:

Borek said:
For each SINGLE ray/photon/wave - whatever we decide to call it - fields vibrate in such a way that B is perpendicular to E and both are perpendicular to K.

This is a picture of a single photon, you have quite a number of photons moving in the same direction, every one with its own E/B fields perpendicular to each other, but not parallel to the fields of other photons. While technically it is possible to draw a thousand photons, each at its own angle, such a picture won't be in any way better.
 
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  • #36
Borek said:
every one with its own E/B fields perpendicular to each other
And also perpendicular to the direction of motion of wave.
 
  • #37
You need to watch the Cosmos with Neil deGrasse Tyson and understand that these discoveries were paramount in the evolution of science. The wave theory was "seen" by Isaac Newton by splitting light with a prism, and infrared was discovery by accident by Herschel (control thermometer). The true nature of spectroscopy wasn't discovery until Fraunhofer magnified the spectrum, seeing the gaps between the spectral colors and to his amazement seeing a code in nature on an elemental level. On the other side, Faraday discovered the effect electromagnetism had on light (observed light pass through glass, a dielectric while creating a magnetic field), which was later backed mathematically by Maxwell. Later Einstein's Nobel prize work on the photoelectric effect put all of this work together and boom, solar panels 50 years later!

"Just as there's a gap between observing something and knowing how it works, there's a gap between knowing how something works and being able to do anything useful with it. "-https://[URL='http://www.theatlantic.com/technology/archive/2014/09/einstein-didnt-win-a-nobel-for-relativity-he-won-it-for-this/380451/']www.theatlantic.com/technology/archive/2014/09/einstein-didnt-win-a-nobel-for-relativity-he-won-it-for-this/380451/[/URL]
 
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  • #38
Gracy,
maybe the analogy to sound is helpful. Sound is also propagating waves. If you press just one key on a piano, you will get approximately a "monochromatic" wave. If you play an accord, this corresponds to polychromatic light (Btw. note, that "chromatic" has a completely different meaning in music). White light is best compared to the noise coming off a radio which is not set to some radio station. So there are lots of frequencies or sound wavelength whose intensity changes quite erratically. In air, the sound waves are just compressions and expansions of the air, so sound waves have no polarisation. In solids, there can also be transversally polarised sound, i.e., the medium is shifted perpendicularly to the propagation direction, just like when you wiggle a rope. Light, at least in air or vacuum, is always perpendicularly polarised. In former times, people thought that electromagnetic waves are carried by a medium too, which they called aether, but gradually they found out, that no such medium exists and that what oscillates in light is the strenght of electric and magnetic fields.
 
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