(comments to: firstname.lastname@example.org)
(CUPS = Consortium
for Upper Level
published by John Wiley)
Modern Physics Suggestions
from the CUPS
- Rutherford Scattering
- Electron Diffraction
- Special Relativity
- Laser Cavities and Dynamics
- Nuclear Properties and Decays
- Quantum Mechanics
- Hydrogenic Atoms and the H2+ Molecule
- Geiger and Marsden used 8.1 MeV alpha particles, scattered from a gold
Calculate the closest approach of such an alpha particle to a gole (Z=79)
Is it within range (10^-15 m) of the nuclear force?
- Calculate the deBroglie wavelength of an 8.1 MeV alpha particle.
Is this large or small compared to the distance of closest approach?
- Run the simulation of the Geiger-Marsden scintillation experiment.
If time is available, get enough points to observe a number of backscattered
(>150 degrees) alphas.
- Repeat the Davisson-Germer experiment. Use the (111) plane and do runs
for accelerating voltages of 40,44,48,54,60, and 64 V. Record the height
of the peak at 130 degrees for each run.
- Beam of particles incident on a barrier. Run the 'barrier' section
of the program.
Observe the qualitative difference when the beam energy is above the 2
eV height of the barrier, and when the incoming beam energy is below the
2 eV barrier height.
Write down what you see for the wave function in each case, and give an
explanation for the difference in behavior.
- Run the 'Uncertainty Principle' part of the program.
Describe what happens to the spread in momentum as you make the particle
Make a sketch of the momentum spread for a 'narrow' and a 'wide' electron
- In 'Geiger Tube Counting', do a run with the default parameters.
Press 'Poisson' to bring up a poisson distribution curve which you can
drag around on the screen. Since the GMT (geiger-muller tube) is 'dead'
for a period after each count, you should be able to explain why the GMT
distribution has a peak which is smaller than would be true for an 'ideal'
- Predict which way must you move the incoming count rate from its initial
value of 250/s so that the ideal and GMT curves will be closer together.
Make the change in count rate, do the run, and record the peak values of
- Change the incoming count rate to 8000/s. Now the counts are coming
in with an average spacing of 125 microseconds. Leave the geiger tube dead
time at 200 microseconds. Do a run and record the peak values of each distribution.
- Does the GMT distribution have the same 'width' as the ideal distribution?
- Bring up the poisson distribution and drag it over to the ideal distribution.
How does it fit?
- Drag the poission distribution over the GMT distribution. How does
- Can you predict the peak of the GMT distribution if the count rate
were set to an enormous rate, like 1 million per second? [ Every time the
tube 'woke up' after being dead, bang! there would be another particle