Recent content by tashi

E.g., if you put lots of point sources in a line, the only constructive interference of each of these spherical waves appears like wavefronts of a plane wave, look at this diagram http://theory.uwinnipeg.ca/physics/light/node3.html

i don't think the speed of sound could ever exceed c because sound requires a medium to propagate through, which contains molecules, and no matter what the medium, molecules cannot move faster than c. Although waves in a wave packet can move faster than the wavepacket itself (propagated by the...

thanks guys. so do electrons have angular momentum then? if so, is this different from their quantum spin number?

so what is spin?

hi, i am trying to work out exactly what is the difference in quantum mechanics between 1) spin, as in 'angular momentum' and 2) spin as in 'quantum spin number'. It seems like quantum spin number only describes certain properties, like whether a particle is a fermion or a...

What is group theory? I looked it up and at first it seemed like another way of manipulating numbers, like matrices or tensors, but then they got into 'classifications of geometry' and permutations and now I'm totally confused.

It's sometimes easier to find the change in energy first (whether +ve or -ve) and decide whether it is positive or negative afterwards. energy lost ===> ΔE is negative ==> work done by system energy gained => ΔE is positive ==> work done on system A good example is the first law of...