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 Sep 24 awarded Autobiographer Oct 21 comment How much photons are needed to erase a complete mountain? Won't work for SiO2 with 532 nm. SiO2 has very low absorption of light with 532 nm. 430 nm is a better choice. Oct 3 revised Ball rolling into a bowl - where is its maximum KE (speed)… given there is friction. See diagram added 5 characters in body Oct 3 revised Ball rolling into a bowl - where is its maximum KE (speed)… given there is friction. See diagram added 43 characters in body Oct 3 answered Ball rolling into a bowl - where is its maximum KE (speed)… given there is friction. See diagram Oct 2 comment Example where angular momentum and angular velocity are not parallel Imagine this, the dumb bell is rotating about a stick. The angular momentum is parallel to the stick. But the stick itself is inclined w.r.t another, stationary, reference axis and is rotating about that axis. The reason for using r parallel to the arms and not the stationary axis is is because r is perpendicular to the axis about which the masses are rotating. But that axis itself is rotating w.r.t another.The angular momentum vector is rotating with respect to the stationary axis. Oct 2 comment Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$ @Ruslan. Isn't that the whole point of tunneling? If the particle has precise energy then it cannot be confined in the well and hence it has a finite probability density outside the well which manifests itself as tunneling. Oct 1 revised Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$ added 232 characters in body Oct 1 revised Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$ edited body Oct 1 revised Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$ added 18 characters in body Oct 1 answered Quantum tunneling effect in a potential of the kind $V(x)=A\frac{x^2}{1+x^4}$ Oct 1 revised Energy of electric field added 47 characters in body Oct 1 revised Energy of electric field added 47 characters in body Oct 1 comment Domain of validity for semiconductor equations I don't see why not. These equations apply to any material with a bandgap. I can't think of any effect that breaks down for large bandgaps as a general rule. Any material specific electronic behavior is contained in the effective masses of holes and electrons. Oct 1 comment Commutator problem Can you please define what the Psi stands for? At fist it looks like you're commuting the hamiltonian with the wavefunction. Oct 1 revised Energy of electric field added 2 characters in body Oct 1 revised Energy of electric field deleted 9 characters in body Oct 1 answered Energy of electric field Sep 4 awarded Commentator Sep 4 comment Double Slit Experiment: How do scientists ensure that there's only one photon? The double slit experiment was performed over a century ago, there were was no nanotechnology back then. So how do you think people made sure that just one single photon was involved in the experiment, other than deducing the existence of light as quanta by the observation of experiments?