4th October 2008 - 10:56 AM
You know Mia. I like your questions.
They are highly perceptive and force me to think.
When you discuss monochromatic light and the two slit experiment you might first want to define the difference between non-monochromatic versus monochromatic and coherent light.
A Ordinary light source overlaps itself with wavelengths as it rarely are monochromatic. That means that they most probably will have a indefinite number of wavelengths present.
"When interfering, waves add constructively or subtract destructively, depending on their relative phase." Also there are no path lengths defined to them from their source.
"Monochromatic light is literally light having one color. More generally it means light having one wavelength. However, it is not possible to isolate light of only one wavelength.
The best one can do is isolate a narrow range of wavelengths.
A working definition of monochromatic follows:
A monochromatic light source is one which emits light over less than 0.1 the range of wavelengths absorbed by a sample.
Thus, if a sample absorbs over a 10 nm range, a source that emits over a 1 nm range is monochromatic.
However, if the sample absorbs over only a 0.001 nm range, a source that emits of a 1 nm range is non monochromatic.
Thus a source that emits over a 1 nm range may be monochromatic is one situation, but non monochromatic in another."
Two waves are said to be coherent if they have a constant relative phase, which also implies that they have the same frequency.
The degree of coherence is measured by the interference visibility, a measure of how perfectly the waves can cancel due to destructive interference.
Laser light is particularly useful for showing interference effects because it is intense, highly monochromatic, and emitted in long wave trains and so maintains a constant phase relationship over large distances. We say that the waves arriving along two or more paths are said to be coherent."
And why do they use lasers monochromatic/coherent light for 'illuminating' their experiments?
My guess would be that they want to eliminate any possible 'interference' from the light itself by keeping it as much as possible to one wavelength/energy quanta.
Also I think it gives you a greater measure of control in time over the photons using a laser, where you can quench and emit them very exactly
The original Young's double-slit experiment was 1801 and there was definitely no lasers then :) the wiki about the double slit experiment.
And Make sure to read this about the original experiment and some strange implications :).
Just wondering here, wouldn't it be possible to, when this light 'interfere' with itself, to measure if the energy would be strengthen at the points of illumination/momentum?
And if treated as particles, don't that mean that they should have 'double' the impact?
"A comment should be added here about widespread misconception about energy and momentum of elementary particles. It is widely taught that photons are supposed
to be monochromatic (state of definite energy and state of definite momentum in
freespace). This statement is completely incorrect.
We can take a photon and place it in a linear superposition of two energy eigen state
(in free space for example). So we can have a single photon whose energy and
momentum are not well defined "
is Avogadro's wiki.
(m and M stands for mass or does M stand for the molar mass constant
I didn't get any sense out of your equation, but hey, no surprise there :)