Light questions (not wave/particle duality)

In summary, the conversation discusses the limitations of the classic one-dimensional picture of light as an electromagnetic wave. The electric and magnetic fields in this picture are only felt along a line, but what happens if you are standing at a certain distance from the axis of propagation? The possibility of a more complex three-dimensional description, such as using Gaussian Beam analysis, is also mentioned. The role of quantum mechanics in describing a single photon is also brought up.
  • #1
Riposte
16
0
The classic picture of light is as an electromagnetic wave. In textbooks you get the nice pictures of eletric and magnetic field vectors bound together at right angles, oscillating on into the distance. However, this is a very one dimensional picture. The electric and magnetic fields would only be felt along a line. What happens if you're standing 1 cm away from the axis of propagation? How about 1 nm? Is there a more complex 3-D description of light as a wave? Even if there is a fast decay in field intensity away from the axis and it can be approximated as 1-D, the familiar vector description seems inadequate to me.

I'm guessing some responses may invoke plane waves, but I am fine with those. It's really only the 1-D description that concerns me. Perhaps, because it's a classical description of a single photon, quantum mechanics must instead be used here, and the 1-D classical description really isn't valid for a single photon? Any other ideas?
 
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  • #2
See posting #6 in this thread, with its attached diagram. It might help you get a better mental picture of a classical plane electromagnetic wave.
 
  • #3
You are correct, a light wave must exhibit a finite 'width', EM waves must possesses a finite width for continuity reasons. This is also the reason why ray analysis (in optics) fails under certain conditions and why you cannot focus a beam of light into an infinitely small point.

A more accurate description of a finite light beam are those described using Gaussian Beam analysis. The scalar expression of the fields I find digestible, but the vector description is somewhat horrendous (you would need to wade through some literature to find it).

More info on Gaussian Beams - http://www.rp-photonics.com/gaussian_beams.html

Claude.
 

What is light?

Light is a form of electromagnetic radiation that is visible to the human eye. It is made up of particles called photons and has properties of both waves and particles.

What is the speed of light?

The speed of light is approximately 299,792,458 meters per second in a vacuum. This is considered the fastest speed that exists and is used as a constant in many scientific equations.

How does light travel?

Light travels in a straight line and can move through empty space or through a medium such as air, water, or glass. It can also be reflected, refracted, or absorbed by different materials.

What is the visible spectrum?

The visible spectrum is the portion of the electromagnetic spectrum that can be seen by the human eye. It ranges from red, with the longest wavelength, to violet, with the shortest wavelength.

How is light produced?

Light can be produced in different ways, including by heating an object, chemical reactions, and through the use of electricity. Some sources of light include the sun, light bulbs, and fireflies.

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