Is there a phenomenon visible to the naked eye that requires quantum mechanics to be satisfactorily explained? I am looking for a sort of quantic Newtonian apple.
[Physics] Quantum mechanics and everyday nature
everyday-lifequantum mechanics
Related Solutions
Why isn't Newtonian mechanics valid in Quantum world?
The answers to "why" questions in physics end up in "because it has been observed to be so"
When science progressed into the realm of the microscopic, of dimensions the size of an atom, i.e. less than a nanometer, it was observed that newtonian mechanics and classical electrodynamics were in contradiction with experiments, could not explain them. For example, they could not explain :
2) The table of elements which showed regularities unexpected by a simple atomic (a la Demokritos) nature following newtonian mechanics and classical electricity
3) The light spectra. The existence of the hydrogen atom which forced the quantum mechanical view finally, because a differential equation was found which completely described the energy levels seen in the light spectrum of the atom. There was no explanation using using classical electromagnetism and newtonian mechanics
4) Interference effects seen in particles, like electrons, as if they were waves: individual electrons passing through slits showed an intensity pattern appropriate to waves not to newtonian particles
Suppose you isolate an alpha particle and accelerate it in absolute vacuum. Why it doesn't follow the equation $F=ma$?
At the microscopic level, forces don't have a meaning, because nothing touches directly anything else. There are intermediate force carriers of what is perceived as "force" macroscopically.
If Newtonian mechanics is invalid in quantum world, what is the guarantee that Quantum mechanics is valid in macroscopic world?
The guarantee that macroscopically the newtonian mechanics and classical electrodynamics appear as we have validated them experimentally is that all of quantum mechanical behavior rests on h_bar, a very small number which is irrelevant for the distances and energies we move and observe macroscopically. There is a smooth mathematical transition from the QM regime to the classical regime.
Best Answer
Use a prism (or a diffraction grating if you have one) to break up the light coming from a florescent bulb. You'll see a bunch of individual lines rather than a continuous band of colors. This comes from the discrete energy levels in atoms and molecules, which is a consequence of quantum mechanics.
If the audience you have in mind is more advanced, you can present the ultraviolet catastrophe of classical mechanics. Classically, something with finite temperature would tend to radiate an infinite amount of energy. Quantum mechanics explains the intensity vs. wavelength curves that we actually see.