What Oscillates in Light and What Are the Units of Measurement?

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Discussion Overview

The discussion revolves around the nature of oscillations in light, specifically what is oscillating in electromagnetic waves and the units of measurement associated with these oscillations. It touches on theoretical aspects of electromagnetic fields and their properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant asks what specifically is oscillating in light, noting the relationship between frequency and energy.
  • Another participant states that the electric and magnetic fields are what oscillate in light.
  • A follow-up question seeks clarification on the units of measurement for these oscillating fields, suggesting a possible connection to force.
  • It is noted that the electric field is measured in N/C or V/m, while the magnetic field is measured in Teslas.
  • A detailed explanation is provided about the oscillation of electric and magnetic fields, using the example of an electromagnet to illustrate how these fields vary sinusoidally and propagate as waves.
  • The discussion mentions the complexity of light sources, indicating that many non-coherent sources contribute to the light wave, while coherent sources like lasers produce uniform waves.
  • It is mentioned that the energy of photons is proportional to their frequency, but field vectors represent macroscopic quantities proportional to the total amount of light.

Areas of Agreement / Disagreement

Participants generally agree that electric and magnetic fields are oscillating in light, but there is no consensus on the implications of these oscillations or the specifics of measurement units, as questions and clarifications continue to arise.

Contextual Notes

The discussion includes various assumptions about the nature of electromagnetic waves and the definitions of measurement units, which may not be universally agreed upon or fully resolved.

nhmllr
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I have a very simple question
We all know that high frequency light has more energy than low frequency
What IS oscillating, though?
What are the units of the x and y axis?
 
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The electric and magnetic fields are what's oscillating.
 
Vanadium 50 said:
The electric and magnetic fields are what's oscillating.

What are those measured in? Force?
 
nhmllr said:
What are those measured in? Force?

Electric field has dimensions of force/charge. The units are N/C OR V/m

Magnetic field has units of Teslas. You can look here to see how a Tesla is defined in terms of other SI units:

http://en.wikipedia.org/wiki/Tesla_(unit )
 
Last edited by a moderator:
nhmllr said:
I have a very simple question
We all know that high frequency light has more energy than low frequency
What IS oscillating, though?
What are the units of the x and y axis?

It might help if you first think of a very low frequency example of this. All EM waves share the same basic properties.
Imagine an electromagnet (straight coil /'solenoid'), switched on. It will have a familiar 'field line' pattern around it like a bar magnet. You could go to a point in space, nearby and draw a line parallel to this field line with length proportional to the field strength (a vector). Now swap the connections. The change will take some time to reach your measuring point but then the field vector will have changed direction. Keep alternating the connections (better still, make the alternations sinusoidal in time) and the (slightly delayed) vectors will vary sinusoidally. It so happens that your coil will also be producing a varying Electric field at your measurement point and this E vector will be at right angles to the H vector. This variation takes the form of a wave, propagating outwards, with the E and H fields at right angles to the direction of propagation.

With light, the same thing is happening - just faster. There is an extra complication for most sources of light and that is the light is produced by many non-coherent sources (atoms and molecules) so the wave at a point in space is a jumble of many different waves at slightly different frequencies but you can treat it, for many purposes (reflection at a surface, for instance) as if it were just one wave, as with a Radio wave. From a Laser, the waves are all 'in step' and we have a coherent beam - just like from a radio transmitter.

Each atom will release a specified amount of energy in the light it produces (a Quantum or Photon). As you say, the energy of each photon is proportional to the frequency. The Field vectors, however, are macroscopic quantities so they will be proportional to the total amount of light.
 

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