Question

in simple harmonic motion why does omega squared equal k/m? where does this come from?

Answer 1

This comes from the differential eqution of the harmonic motion. The model for a spring, with mass m and elastic constant k, says,
\[m\cdot a=-k x\Rightarrow m\frac{d^2x}{dt^2}+kx=0\Rightarrow \frac{d^2x}{dt^2}+\frac{k}{m}x=0\Rightarrow \frac{d^2x}{dt^2}+\omega^2x=0\]
Using the last substitution is easy to find the solution
\[x=A\cos(\omega t+\phi)\]

Answer 2

i dont understand polarization of x rays plz help me

Answer 3

i want notes on fermi dirac statistics

Answer 4

You can find some interesting notes about Fermi Dirac statistics in the web. For example,
http://solar.njit.edu/~leej/lecture/ph641/Ch04_summary.pdf
However, I also reommend you the Volume 5 of Berkeley Physics Course (introductory level) and the book from Kittel "Elementary Statistical Physics", Part1, Chapter 19. Other books of higher level (Hwang, Pathria) should be usefull too.

Answer 5

For X-ray polarization you can check the following links,

http://skullsinthestars.com/2009/06/06/barkla-shows-that-x-rays-have-polarization-1905/

http://www.nist.gov/pml/div684/grp01/x-ray-polarization.cfm
http://www-conf.slac.stanford.edu/xray_polar/X-Ray%20presentations/Fabian.pdf