Recent content by phrygian

  1. P

    Transfering? And I'm Lost!

    I am currently a first year graduate student in physics and am working on external fellowship applications. With most applications being due in the November - December range, I will have only been working with my current advisor for one or two months at the point where I would have to ask for a...
  2. P

    Graphene ambipolar field effect

    In graphene the fermi level can be moved into the conduction or valence bands by applying an external electric field, allowing conduction by either holes or electrons. My question is where do these new electrons come from (or go to in the p-type case)? Also, why is this special to...
  3. P

    Why so much energy?

    What is the advantage of the higher energy of the LHC for finding the Higg's when Tevatron was already operating at an energy significantly higher than the predicted Higgs mass? Is it just that higher energy collisions will result in more particles, making data collection faster?
  4. P

    Transmission Line Impedance Matching

    In the case of a complex source impedance ZS and load impedance ZL, maximum power transfer is obtained when ZS = ZL*. For a lossless transmission line terminated on one end with a purely resistive load, zero reflection is obtained when ZS=ZL. What about the case of a lossy transmission...
  5. P

    Reflection at a conducting surface

    In Griffiths Electrodynamics (page 397) electromagnetic wave reflection at a conducting surface is introduced. He says "for ohmic conductors, Jfree = sigma * E, there can be no free surface current since this would require an infinite electric field at the boundary." I don't understand why...
  6. P

    Eye floaters Fungus

    But what can you say about the picture I linked to? Are there many different biological materials that could produce such shapes or does that characteristic of something in particular?
  7. P

    Eye floaters Fungus

    Eye floaters are debris in the eye's vitreous humour, which seem to float over your vision and are extremely annoying. When using an optical microscope my floaters become extremely clear against the bright background I am viewing, and what I see looks almost exactly like this...
  8. P

    Why the rush for papers?

    As an undergrad, I understand my motivations for my group publishing papers: that my name could be on one which would help me get into grad school; similar to the motivations of an assistant professor hoping to get tenure. Everyone I meet seems in a rush to get good results and publish them...
  9. P

    Electron hole pair

    When an electron in a semiconductor is excited to a higher state, an electron hole pair is created. How does this not violate charge conservation, a charge of +e turns into a net charge of 0? Thanks for the help
  10. P

    Trying to understand the Brillouin zone

    I am having a really hard time understanding how the Brillouin zone relates to electron states and have a couple of questions that might help clear it up for me. For a band structure like this: [Broken] I know that the...
  11. P

    REU with research experience.

    I go to a big school with lots of physics research available. I started in a group at the beginning of this year, and I'm a junior and have good grades. From looking on different REU program websites it seems like a lot of them seem to want people with limited access to research at their...
  12. P

    3D Electron Gas Derivation

    But wouldn't that give 1/(2pi)^(3/2) since the x, y, and z waves each contribute 1/(2pi)^(1/2)?
  13. P

    3D Electron Gas Derivation

    Homework Statement In a solid state book I am reading the 3 dimensional electron gas is derived. It says, "An unconfined electron in free space is described by the Schrodinger equation where m is the free-electron mass. The solutions of the equation, phi(r)=1/(2pi)^3 Exp(ik.r) are plane...
  14. P

    Adding vector components

    It's problem 4.50 in griffiths quantum mechanics and here is a quote from the solution manual: We may as well choose axes so that a lies along the z axis and b is in the xz plane. Then S(1)a= S(1)z , and S(2)b = cosθ S(2)z + sinθ S(2)x . S(1)a means the spin operator of particle 1 in the...
  15. P

    Adding vector components

    What I mean was Ax Sin(theta) + Ay Cos(theta) = A where A, Ax and Ay are vectors, I don't see where this relation comes from?