Search results

  1. J

    Studying Quantum Information and Computing

    I have just finished my 2nd year of undergraduate study, which had the first pass of QM in it. I want to do a PhD in Quantum information/computing. What can I learn in my own time to get me closer to understanding QM information/computing? Currently I only know what we covered in lectures, and...
  2. J

    Coefficients of a particle in Linear superposition (QM)

    1. Homework Statement a particle is in a linear superposition of two states with energy E_0 \ and\ E_1 |\phi> = A|E_0> + \frac{A}{(3-\epsilon)^{1/2}}|E_1> where: A \ > \ 0, \ 0\ <\ \epsilon \ <\ 3 What is the value of A expressed as a function of epsilon 2. Homework Equations P(E_0) \...
  3. J

    Electron changing energy state

    When a photon is absorbed by an electron the electron moves from ground state to a higher energy lets say n=3. this electron can then drop back down and emit a photon of the exact energy as the photon that was absorbed. My question is why is there no work function or energy transfer as it...
  4. J

    Diffraction grating of laser light

    1. Homework Statement a narrow beam of laser light (i.e coherent monochromatic light) wavelength 630nm is incident on a grating having 300 lines per mm. a piece of paper is curved 180 degrees beyond the grating. calculate how many spots of red light should be seen 2. Homework Equations...
  5. J

    Potential difference in parallel circuit

    1. Homework Statement I am currently revising some AS level Circuit modules and i'm having trouble seeing how the P.D across 3 components in a parallel circuit can each have the same value as the P.D of the battery. I am probably just being dumb but its just not making sense! such as this...
  6. J

    Destructive Interference and coherent light in anti-phase

    I have a question about coherent light in anti-phase, I'm probably thinking about this wrong but I just cant understand what happens to the energy in the wave when two waves of the same wavelength, frequency and amplitude are in anti-phase as the resultant wave is 0.
  7. J

    Light as a wave

    I am currently studying AS level physics and we have just started the waves module. When describing light as a WAVE our teacher is telling us that particles are oscillating 90 degrees to the propagation of the wave. What is acting at right angles to the propagation of the wave? As far as i was...
  8. J

    Energy level after photon absorbtion

    Say a photon was absorbed by an electron at 1s in an oxygen atom but it only had enough energy to move it to another energy level that was already occupied such a 2s etc. What happens to this photon?
  9. J

    White light and how it works

    I have been thinking about white light and having some trouble visualising how it actually works. I am aware that white light is made up from all the colours of the visible spectrum, my question is how does the light travel together in wave and photon form? my only thoughts so far are that...
  10. J

    Derive V2=u2+2as

    So i am having a slight problem deriving this equation. there is a simple way which is v=u+at -> t = v-u/a s = (v+u)t/2 so s = (v+u)*(v-u)/2a 2as = (v+u)(v-u) 2as = v2-u2 v2=u2+2as but i am having trouble understanding this way V2=(u+at)2 V2=(u+at)(u+at) V2=u2+a2t2+2uat - i cant...
  11. J

    Why is a hydrogen atom lighter than a electron and a proton

    What exactly is it that makes the energy/mass of a hydrogen atom be lower than that of the electron and proton separately? I am aware that this process is what causes stars to emit light, during nuclear fusion deuterium has a smaller mass than a proton and a neutron so its extra mass/energy is...
  12. J

    Cesium radiation per metre

    I am reading a book called advanced physics, which is very good I may add. there is a question in it as follows; The second is defined as 9,192,631,770 periods of radiation from a caesium-133 atom, The metere is defined as the distance travelled by light in 1/299792458 of a second. How many...
  13. J

    Momentum or Earth?

    Momentum of Earth? Earlier I was thinking about circular motions and centripetal forces and the earth around the sun, If p=mv and the velocity of a object in circular motion is constantly changing does this mean Earth's momentum is constantly changing? or is it that earth is travelling on a...
  14. J

    Drift velocity

    1. Homework Statement a wire carrying a current of 3.2A has a radius of 1.2mm. the material of the wire has 2.5x10^25 free electrons per cubic metre. the elementary charge is 1.6x10^-19 2. Homework Equations I=Anev cross section = pi*r^2 3. The Attempt at a Solution...
  15. J

    A Clear LED emitting different coloured light?

    Am I right in thinking the chip controlling the LED is applying more or less power to make electrons go to different energy levels to emit different colours of light? If any one could clear this up for me it would be much appreciated.
  16. J

    White dwarfs and degeneracy

    Yesterday i had a thought about when our sun runs out of energy and collapses into a white dwarf, it is my understanding when this happens a white dwarf is held up by electron degeneracy, all the electrons are under immense pressure but cannot fall to the lowest energy state therefore stopping...
  17. J

    Energy levels and quantum state

    Would any one be able to explain s,p,d,f in detail without using complex math? Also quantum states such a m,l etc. or link me to a site/paper that does? thanks
  18. J

    Period of oscillation for a pendulum

    1. Homework Statement The aim of the experiment is to find out if the period of oscillation is proportional to the square root of the length of the pendulum. We used 5 different lengths and got the average time for 1 oscillation for each length These are the results: Length=48cm, Time=1.33s...
  19. J

    Red flickering of star?

    so I was just looking up at the sky, as you do... and I noticed one star was flickering red, I believe it was betelgeuse - as far as i could see on my sky map app. Could any one tell me the reasoning for this flickering? as none of the other stars visible were doing this - at least as far as i...
  20. J

    How Ionic bonding takes place?

    Hey all, So i am aware that ionic bonding is the giving/recieving of electrons between atoms to form a compound. My question is what is it that makes the electron "move" from one atom to the other, I know that once the electron has moved the atom it came from becomes positively charged and the...
  21. J

    Some advice to become a quantum physicist

    some advice to become a physicist hey all i am from england so some of the posts here dont really apply to me as things are quite a bit different over here in terms of education, i am currently at college which is equivalent to high school in america i believe. i plan on doing physics maths...