Quantum Mechanics demystified, a try
By Googling one finds a lot of descriptions of electromagnetic wave being transversal sinusoidal orthogonal wave propagating through Universe’s spacetime. All that information is essential in analysing behaviour and effects of these waves. And is enough if one wants just to calculate using Maxwell’s Equations to produce real world applications.
If one instead wants to comprehend what’s underneath all that, that’s not so clear at all.
Here I try to dig into this from more philosophical perspective.
Shortly said, electromagnetic waves are disturbances in the electromagnetic field.
Consists of two distinct fields, electric and magnetic, living in strict orthogonal synchronized co-operation with each other. For clarity, I will focus only on the electric field here, but things apply to magnetic one in concurrence.
What’s the disturbance in the electric field then? How could that be depicted?
Think of a large cube full of jelly kind of material. Each point in that cube can be tracked. Let this cube be our electric field.
On the sideplanes of this cube one is able to vibrate any point along the plane to make it move ahead and back in one direction, which direction becomes polarity of the wave. Let this be our source for the EM radiation. Like vibrating electron on atom’s shell or radio antenna or whatever.
This makes adjacent points in sequence inside the cube to do same vibration in kind of hydraulic manner. Like as if a rope would wave through the cube. Speed being that of light. Wavelength depending on the pace of the vibration. Direction may be into any direction through the cube depending on the original vibration. Polarity remains the same throughout the propagation, or polarity would be rotational if originating vibration rotates.
Think of this waving rope presenting a single disturbance in the electric field. Entire electric field is saturated by myriads and myriads of these fluctuations as if each sideplane of the cube had enormous number of source points for perturbations.
Now think of a case where we would vibrate a point at one sideplane only once. A single crest and trough would travel through the rope. That’s a single photon!
From here on, let’s focus on the single photon case, traveling as a single trough-crest pair in electric field.
This single disturbance on the field depicts the force a charge would experience had it been on the spot where the disturbance is passing. Let the electric field be otherwise totally empty except for the disturbance caused by our single photon.
Charge is $e$ and frequency of the photon $f$. Energy associated with the photon would be $E=h\cdot f$. This energy shows up as an electric field of $\vec{E}=\frac{F}{e}$ at the impact. What is strength of the force, that’s not straightforward to calculate, it’s depending on top of the energy itself also on intensity and energy density of the medium.
Anyway, if the force ends up being big enough and polarity of the photon is spot on, electron gets excited and the photon disappears.
Polarity being correct have to do with the direction of the disturbance being properly aligned with atom’s orientation in the molecule and material in question.
Getting back to a sole wave, beam of light. It consists of consecutive trough-crest pairs. Energy of this beam being $E=h\cdot f$. Which energy is enough to excite a single electron in proper material with every trough-crest pair i.e. every $\frac{1}{f}$ seconds.
It is the frequency of the wave that solely defines whether energy is high enough to make an electron excite. Having consecutive trough-crests bombing material for a some time, or having a bigger bunch of coherent photons hit the material simultaneously, doesn’t have an effect if the frequency is not adequate to produce sufficient energy for the material in question. Having larger number of energetic enough photons, consecutively or simultaneously, makes a larger number of electrons excite, though. This is what we perceive as intensity of light.
Editor’s Note!
couple of latter chapters should probably be dealt with in articlkes for what’s light and/or polarization.