Quantum Mechanics Answers

How can I multiply the initial density matrix by the time evolution (U) to get the density matrix at any time ?

explain the physical significance of wave function

what is a photon?

Assume that an electron is located somewhere within a region of atomic size. Estimate the minimum uncertainty in its momentum by assuming that this uncertainty is comparable with its average momentum. Estimate the average kinetic energy of the electron.

is there any electric or magnetic field around photons (like em waves)? and if yes,what are their directions?
thanks a lot!

I'm doing an assessment on the photoelectric effect, and I would like to use your article for information. I was wandering if you could tell how to reference your article, its called "Where Could Photoelectric Effect Lead to?"

what is the schreodinger wave equation?

Prove that if an operator commutes with any two components of J it
must also commute with the third component.

If an atom is placed instead of electron in compton experiment what would happen?

A laser delivers pulses of 2mJ at wavelength 633 nm with a pulse duration of 200 ps.
(hint E=h.c/l, with h=6.6 x10-34 J.s and c=3x108 m/s and 1 eV=1.6 x10-19 J)
i) How far do they travel in 1s?
ii) What is the photon energy in eV?
iii) How many photons are delivered per pulse?

& please show working out