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  1. J

    Possibility of pair Production without interaction with matter?

    1. Homework Statement Is it possible for pair production to occur without interacting mwith matter? 2. Homework Equations E+ + E- = E(gamma) - 2*m_e*c^2 3. The Attempt at a Solution In the Coulomb field of nucleus (or electron), the incident photon energy can be converted to...
  2. J

    Equations of motion and proper Significant Digits.

    1. Homework Statement Solve the following to the proper number of significant figures: a) A loaded truck has mass (2.12 X 10^4 +/- 6 X 10^2) kg and when empty, it has a mass of (1.72 X 10^4 +/- 5 X 10^2) kg. What is the relative uncertainty of the mass of the gravel dumped from the...
  3. J

    Near Normalization calculation for given wavefunction

    Near "Normalization" calculation for given wavefunction 1. Homework Statement A wave function is given by Y(E) = CEexp(-E/kt) 1. Find C so that Y(E) becomes Y0 where Y0 is a constant. 2. Calculate the mean energy with respect to Y(E). 3. Find Y(t) as a function of wavelength...
  4. J

    Schools Thought about graduate school and

    Thought about graduate school and.... I am a senior undergraduate student in Physics (last year is in progress with a GPA that is very close to a B+)..have been around these forums for nearly 2 years now and would like to ask a few questions regarding post-undergrad opportunities. I am...
  5. J

    Spatial filtering

    I am confused by this Abbe thoery thing involvign the use of an optical computer. A laser is focused onto a 10 μm screen with adjustable micrometer screws. A pinhole is provided to avoid any unnecessary dispersion of the laser beam. The first lens converts spherical wavefronts into plane...
  6. J

    Lock In Amplifier

    Is there a book or website that explains throughly how to use a Lock In Amplifier? I have never used one before and am using it in a Johnson Noise experiment with the "Art of Experimental Physics by Preston and Dietz" acting as the lab manual.
  7. J

    .tex file won

    I am trying to open a .tex file. When I clicked on it, it asked what program I wanted to use to open the thing. So I selected wordpad. The thing opened up in wordpad with a blank document. When I selected print preview, it allowed me to scroll through 4 blank pages. Here' s the...
  8. J

    Can the logical state really be determined during this time?

    Using a 555 timer (square wave input) as a NOT gate, can the logical state (0 or 1) be determined during rise and fall times? I would think that this is some kind of discontinuity during which the properties of the wave are not known but am not very sure about the logical state thing. It is...
  9. J

    Underdamped oscillations in an LC circuit

    A square wave pulse (generated using an oscilloscope) is used to induce damped oscillations in a circuit that consits of an inductance L and a capacitance C connected in series. A resistance is present even though no resistor is present in the circuit. a) Find the differential equation for...
  10. J

    A Fourier Optics experiment

    I've been reading some stuff on Fourier Optics (Johnson, Optics) and have become quite interested in how Fourier transforms can be used to explain so much. But I have stumbled on something thta is confusing me. Two students perform a "Fourier Optics" experiment to explore Fourier transform...
  11. J

    Special geostationary orbit condition

    For geostationary satellites moving in circular orbits in the equatorial plane, there is no distinction between the true anomaly f, the mean anomaly M, and the eccentric anomaly E. For geostationary satellites, the angles \theta=Greenwich sidereal time, \Omega = longitude of ascending note...
  12. J

    Still a semi conductor?

    Two students performing a Hall voltage measurement using germanium as a semiconductor reversed the magnetic field while holding the bias current constant but did not get opposite signs for the Hall voltage. The magnitude of Hall voltage detected using a voltmeter was the same as it must be...
  13. J

    Working of a Hall Probe

    Where could I find out how a Hall probe works? I have got a book in mind called Introduction to electronics by Theodore Korneff but am not sure how useful it will be. I have searched the web but cannot find a description of its working. :cry: James
  14. J

    Polynomial fit using EXCEL

    I performed a fit, using EXCEL, to data and the fit gave me a polynomial. How do I get the uncertainty in the resulting parameters. For example the least squares fit gives y = Ax+B and there are equations to give the uncertainties in A and B. IS there a program that does this for non linear...
  15. J

    Practical application for germanium sample

    I just did a semiconductors experiment involving the Hall effect and a doped germanium sample. The type of doping was determined from the Hall voltage using the sign of the recorded voltage and the sign of the bias current applied across the sample. Now, my question is what could be a...
  16. J

    How to stop a fast moving electron

    How much iron is required to stop a 500 GeV electron if it only deposits energy via ionization? Is the following approach correct? E = E0*e(-x/x0) x0 = 170*A*density/Z^2 x = ? where x is the stopping distance E0 = 500 GeV E = 0.511 MeV Or should E and E0 be flipped...
  17. J

    Perturbation of hydrogen energy due to nucleus

    Consider the ground state of the hydrogen atom. Estimate the correction \frac{\Delta E}{E_1s} caused by the finite size of the nucleus. Assume that it is a unifromly charged shell with radius b and the potential inside is given by \frac{-e^2}{4\pi \epsilon b} Calculate the first order...
  18. J

    Particle physics - absorption length

    1) What percentage of incident photon radiation passes through 5 mm of material whose absorption coefficient is 0.7 mm^-1? What is an absorption length? I am lost here. Any input ...some mathematical formula for the absoprtion coefficient.....would be a great help to me. 2) Why is the...
  19. J

    Symmetries in Particle Physicsconservation laws

    Assign specific lepton generation numbers and distincguish between antineutrinos and neutrinos for the following reactions. Make appropriate fixes to show that you know about all the conservation laws not just lepton number conservation \mu -> e^{-}\nu \nu \nu n -> e^{-}p \tau^{-} ->...
  20. J

    Paper on neutrino mass ?

    I am in my senior year of undergrad studies and would like to read a research paper on the NEUTRINO MASS. I am hoping for it to be at a level which I can understand. I am taking particle physics right now. Are there any sites that would offer such documents? James
  21. J

    High Tc superconductivity

    :rolleyes: :confused: How would you explain the V-I curve for High Tc supercondctors? I am reading a section on this topic although we haven ;t studied it and am confused as to how one can explain the curve? It starts off linear then has a flat region and then is linear again. What would...
  22. J

    Conversion to SI units

    How do I convert 2.07*10^-15 Wb in MKS units into SI units? James
  23. J

    Tricky mean life question (potassium)

    Natural potassiu, has an atomic weight of 39.089 and contains 0.0118 atomic percent of the isotope 19 K 40, which has 2 decay modes: 19 K 40 -> 20 Ca 40 + beta particle + neutrino (nu bar) 19 K 40 + e- -> 18 Ar 40 * + beta particle + neutrino (nu no bar) where 18 Ar 40 * means an...
  24. J

    Perturbation theory

    For the harmonic oscillator V(x) = \frac{1}{2}kx^2, the allowed energies are E_n=(n+1/2)h \omega where \omega = \sqrt{k/m} is the classical frequency. Now suppose the spring constant increases slightly: k -> (1 + \epsilon)k. Calculate the first order perturbation in the energy. This is 6.2...
  25. J

    Rutherford Scattering

    Calculate the Rutherford cross section for a 10 MeV alpha particle scattered at firstly an angle greater than 90 degrees and secondly for an angle greater than 10 degrees. What does the relative magnitudes tell you in relation to the probabilities of the momentum transfer at large and small...
  26. J

    Tricky error calculation

    How do I calculate the uncertainty of q = [exp(x/2)][t^(1/2)] where both x and t have known uncertainties. I could have done the thing if there was no exp(x/2) term. But that term is causing me a lot of stress. Can someone please help me. I am really confused. James
  27. J

    Tricky Probability density

    Will P(r) depend on time? Explain your reasoning. The wavefunction is \frac{1}{\sqrt{2}} (\psi_{2,1,-1}+\psi_{2,1,1}) \frac{1}{16}\,{\frac {r{e^{-1/2\,ra}}\sin \left( \theta \right) \left( {e^{-i \phi}}-{e^{i\phi}} \right) \sqrt {2}\sqrt {{\pi }^{-1}}}{\sqrt {{a}^{3 }}a}}...
  28. J

    Dreaded WKB problem

    Consider the potential V(x) = \beta x for x \geq\ 0 V(x) = 0 for x < 0. Find the exact and WKB wavefunction for the situation where a particle has E = 10 in units where \beta = \hbar = m = 1. Any suggestions guys? James
  29. J

    Gibbs sum

    Gibbs sum DILEMNA Consider a system that maybe unoccupied with energy zero or occupied by one particle in either of two states, one of energy zero and one of energy \epsilon_{0}. Allow the possibility that the orbital at 0 and at \epsilon_{0} may be each occupied by one particle at the same...
  30. J

    Quantum mechanics in DIRAC notation

    Consider a particle in a harmonic pscillator potential V (x) is given by V = \frac{1}{2}m\omega^2 Also \hat a = n^\frac{1}{2}|n-1>, and \hat a\dagger = (n-1)^\frac{1}{2}|n-1> where \hat a = \frac{\beta}{\sqrt 2}(\hat x + \frac{i\hat p}{m\omega}) \hat a\dagger =...
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