Home Discussion Forum What is Planks quantum theory of light in simple terms?

What is Planks quantum theory of light in simple terms?


  1. Light is usually thought of to be in wave-form. However, Plank suggested that at a quantum level, light can be broken up into little energy packets. For example, – – – – – -. Those dotted lines are the little “energy packets” within a wave of light. Those packets are now known as photons.
    Regarding Black Body Radiation, materials that are completely black absorb all light. This causes electrons within the black body to move along a cluttered path forming an electron current of sorts. When these electrons collide with one another since its so cluttered, their kinetic energy is turned into heat energy. This is a direct effect to the Law of Total Conservation of Energy.
    Hope this helps!

  2. The QTL simply says that light comes in little bundles of energy that eventually became known as photons. Each photon has energy e = hf = hc/L; where h is Planck’s constant of proportionality that was found through repeated lab experiments with photo electric material. A. Einstein won his Nobel Prize in Physics for his work in confirming the QTL. Let’s dissect the quantum energy relationship and learn a bit of physics.
    e = hf = hc/L; where f is the frequency of the light, c is light speed, and L is the wavelength of the light.
    The first thing we see is that the energy of a photon goes up and down as its frequency goes up and down. So in the ROYGBIV rainbow colors, we can conclude the Red light is a lower energy light because its frequency is lower and the Violet light is a higher energy because its frequency is higher.
    The second physics fact is that f = c/L, which says the frequency of light is inversely proportional to its wavelength and, ta da, the constant of proportionality is exactly the speed of light. So, for example, when we operate a radio in the L = 1 meter band, we know we just tune the receiver to f = c/L = 3E8/1 = 300 MHz or thereabouts as light speed is about 300 million meters per second.
    The third thing to note is that e = hf applies to all electro magnetic (EM) photons, from gamma rays at the extreme high energy end down to very low frequency (VLF) radio emissions a the extreme lower end. The frequency band for visible light is somewhere in between these two extremes. (Note that VLF and gamma rays are strictly arbitrary cut offs. In fact the spectrum could run lower and higher than these extremes.)
    And that’s the QTL: e = hf. That’s about as simple as it gets.

  3. It was thought that light creates a continuum. That is that light can occur at ANY frequency, difference between Real numbers and Integers…
    …Raleigh (I think) showed that given a continuum that classical physics (assuming light is a continuum) predicts that the energies you see emitted (due to thermal collisions) would become infinite as you probed the higher and higher frequencies.
    …This may be difficult to fully understand, but basically the theory (old theory) predicted (obviously incorrectly) that if you were to measure the frequency given a “blackbody” (virtually everything is a blackbody, the Sun is pretty much purely a black body) then as you started probing higher frequencies the theory predicted that the amount started INCREASING…obviously in real measurements there was a peak wavelength…higher energy (lower wavelength) corresponds to hotter bodies. But there is a peak, then as you get higher (or lower) it reduces to essentially 0 (amount).
    So Plank was trying to solve this problem and when we made the assumption that instead of a continuum, that light came in integer multiples of a constant (h = 6.63*10⁻¹⁶ eV*s…this means that for 1eV bandwidth of energies there exist 1/h ~ 10¹⁶ different wavelengths available to fill this width of energies…so of course it appears continuous to us)
    When he redoes the calculations using this quantized energy model, he gets results that match the experiment VERY closely…leads to quantization of energy…wave (or quantum) mechanics may be ultimately motivated by Plank, but the two are VERY different things…that is what Plank discovered and what Quantum Mechanics is are not very closely related.


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