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Quick fun analogy: If we think of the expansion of space as a sheet stretching, particles of matter move away from each other. Hooray, as explained several times before. Extending this to 3D, we're basically stretching objects at a very slow rate. 1.62038964 × 10^-17 m/s / meter, to be precise. Thus, a typical person is stretched at about 3x10^-17 meters ...


An intuitive explanation could be that the photon has a longer road to be traveled in a medium?


If you want to prove an isolated atom is spherically symmetrical, you could proceed by showing the sum of the probabilty functions (wave functions squared) of each orbital results is a spherically symmetrical distribution. Certainly s-orbitals are spherically symmetrical. The sum for an entire subshell of orbitals (such as all three 2p orbitals) is ...


Graphene is only transparent because it is very thin (one atom thick). If it absorbs 2% per layer then just a few hundred layers would absorb almost all light and that would still be a very thin sheet of graphite. The question should be why does graphene absorb so much light compared to diamond which really is transparent? A simplified answer is that ...


I assume the biggest factor is the thickness. Graphene is a layer of carbon one atom thick. Light is absorbed/reflected by the top layers of a material and if you make any material into a layer one atom thick you'll find it increases transparency a lot. The thing that is special about graphene is that it forms bonds in a 2D layer where most materials ...


What makes Graphene so strong is its electrostatic forces resulting from delocalized electrons flowing through positively charged carbon atoms. This diffrence in charge creates a strong electrostatic attraction that holds Graphene together. This phenomenon also explains why it is such a strong conductor.


The reason is because there are no particles at the 1eV level to absorb the energy. In the ground state, all the particles are at the lowest level.


As soon as you lose the idea that only "mass" can legitimately fill something, then there is no "empty" anywhere. Even a vacuum is not empty.


Imagine you have a house, and you have a dog in that house, and you left in the morning. You are now standing in front of that house. Is the house empty? From one point, you could say Yes, the house is 99% empty, only 1% of it is filled with dog, and not air. But then, give me an example of a place with no dog. Alright, you say the bathroom. Bzzt. There is ...


Atoms can interact in a variety of ways, it varies from experiment to experiment. In principle two qubits with spins 1/2 could interact via magnetic force. In this case they would have to be extremely close. This experiment would also be extremely hard. An easier way would be to use ensembles of atoms. Atomic beams can be prepared where atoms are held in ...


It's because there are alternating layers of + and - ions in the c-direction, yielding a dipole in the crystal. See Tasker -- http://www.surface.tulane.edu/teaching/classnotessurface/TaskerJPhysC79.pdf


Both electric and magnetic field apply a force on charged particles (roughly saying this is not always valid as you will see in case of magnetic field.) It's a vast topic but I would summarize it quickly, note that the explanation here involves mostly non-relativistic (small speed in comparison with light where things change drastically) explanation: ...

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