Not all of these are guaranteed to be available. Necessary equipment may be broken, missing or in use elsewhere. I reserve the right to assign specific experiments to specific individuals. THIS LIST WILL CHANGE...
I strongly encourage you to develop your own experiments. Please discuss your ideas with me.
|Charge to Mass ratio of Electron|
|Half-Life of 137m Ba|
|Helmholtz Pairs: B and dB/dz|
|Gamma ray spectroscopy|
|Impedance of a speaker system|
|The Hydrogen Spectrum|
|Resistivity vs. Temperature|
|Temperature Dependence of Diodes|
|Black Body Spectrum|
|Charge on the Electron (Millikan Oil Drop)|
|The Universal Gravitational Constant|
|Anything you come up with that I like|
Determine e/m, the Charge to Mass Ratio of an Electron
An electron with known energy in a uniform magnetic field moves in a circular path. Measurements of relevant parameters allows you to determine the quantiy e/m for the electron. We have an apparatus dedicated to this experiment.
The Half-Life of 137mBa
This relatively short-lived excited isotope of Barium emits a gamma ray which can be detected by a Geiger–Mueller detector. Measuring the decay rate of a sample of Barium will enable you to determine its half-life. You will need to determine the operating voltage of the tube by first determining the plateau region. The curve you plot for the sample of 137mBa should show an exponentially decaying count rate. From this you can calculate the time it takes for the decay rate to drop by a factor of two, the half-life.
Since the 137mBa has a short half life we must have a continuous supply handy in the lab. We have a generator which contains some 137Cs, which continuously produces the Ba we need via radioactive decay. We extract some of the daughter nuclide 137mBa and put the radioactive solution into the G-M counter. I will show you how to do this. Observe appropriate caution (gloves and goggles) when extracting the sample.
You will need to measure and correct for background radiation. Ask yourself, "Is my data an exponential decay?" What features, usually apparent with some simple mathematical operations, should it have?
There are many statistical aspects of radiation that bear investigation. The distribution of actual activity about some average value for the case of "constant" activity is interesting. Gaussian versus Poisson statistics also comes up.
Determine the Impedance of a Speaker
We have a variable frequency power supply and a function generator that you can use to determine the impedance of a coil as a function of frequency. Might be good for audiophiles.
Microwaves are electromagnetic radiation, as is light. They are subject to the same set of rules and phenomena that light is. You can make a microwave lens, diffraction grating, and even measure the index of refraction for microwaves in a medium via Snell's law. Measure the brewster angle of microwaves for several materials, thus determining the index of refraction for each.
Temperature dependence of resistivity
Measure the temperature dependence of resistance for something interesting, perhaps some wire, a resistor or a lightbulb. This likely would use the lock-in amplifier.
Temperature Dependence of Diodes
Investigate the temperature dependence of the current-voltage (I vs. V) characteristics of some diodes.
Hydrogen Spectrum and the Rydberg
There is a simple relationship between the quantum numbers of an electron in a hydrogen atom and the wavelength of a photon emitted or absorbed. This relationship uses the Rydberg constant, whose value was known from experiment well before we had any clue about the structure of the atom or the Bohr theory of the atom.
You will use a relatively simple table-top spectrometer and gas discharge tubes to measure the wavelengths of emission lines. You may use a gas other than hydrogen to help you calibrate the spectrometer. Look up in a modern physics book the explanation and the math. The NIST Atomic Spectra Database lists thousands of spectral emissions and is searchable by element and wavelength range.
Traditional Helmholtz coils have advantages with respect to easy achievement of uniform magnetic field and uniform field gradient, dB/dz. Investigate these features using our Hall probe for magnetic field measurement, and make corrections for the non-ideal nature of the coils.
The Charge on the Electron (Millikan Oil Drop)
We have the Millikan Oil Drop apparatus. You squint through a microscope and watch oil drops. If you apply an electric field, and the droplet is charged, you can counteract gravity with an electric force. The end result is that you can determine the charge on a single electron. Check out the description of this experiment in the Modern Physics book. Also, see this description.
Determine the Universal Gravitational Constant
Read up on the original Cavendish experiment in which he determined the value of G. This is a very similar experiment, except you can use a laser-based light lever to aid in measuring the very small deflections of the torsion pendulum.
Find something interesting and clever to image/characterize/analyze using the electron microscope
Investigate the spectrum of the plasmas in our H and He spectrum tubes. Expect that there will be differences in the spectrum as a function of place in the tube you collect the emitted light from. Perhaps use a variac to change the excitation voltage (but check with me first, as this is a partly-baked idea and it depends on the nature of the regulation in the tube power supply). This will require using one of our fiber-optic spectrometers. Plasma
Black Body Spectrum
Investigate the spectrum of an approximately black body. Compare it with the predictions of the Planck radiation law. This will require using one of our fiber-optic spectrometers.
Using a lock-in amplifier set up an experiment in which you make some useful (or at least interesting) measurements. There are possibilities for measurements of optical properties or electrical ones at least. A little research should turn up something that you find interesting.
How does the response to a periodic input depend on the bottom profile of a body of water? Are the resonant frequencies for water sloshing around measurably different? What other effects might you measure?
Gamma Ray Spectroscopy
We have computer controlled apparatus for this. You may find useful info at the LBNL, or at the Decay Data Search Site.
Fluid Dynamics: Reynolds number and viscosity
If you find fluids interesting, you could do something involving Reynolds numbers, or viscosity of a fluid, temperature dependence of viscosity...
Updated: 12 Jan 2012