2011 Short Form Catalog

Instruments by Course Title

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diode laser spectroscopy

earth's field nmr

earth's field nmr gradient/field coil system

fabry-perot cavity

faraday rotation

hall effect

magnetic force

magnetic torque

magnetic torque's magnetic force balance

modern interferometry

muon physics

noise fundamentals

optical pumping

power/audio amplifier

pulsed/cw nmr

pulsed nmr

quantum analogs

signal processor
/lock-in amplifier

sonoluminescence

torsional oscillator

two slit interference, one photon at a time

two slit's cricket

individual parts

TeachSpin's Faraday Rotation Apparatus, FR1-A, Includes:

• The Light Source
The Solenoid (magnetic field source)
• The Analyzer Polaroid
• The Optical Detector

The Light Source
The light source is a red laser pointer operating at a nominal wavelength of approximately 650 nm with a power output of about 3 mw. It requires a voltage regulated supply of 4 volts and 40 mA. TeachSpin’s Power Audio Amplifer PAA1-A has a voltage regulated (4V) supply output specifically designed for this laser diode light source.

Although the output is approximately 60% polarized, the laser light is directed through a polarizing filter which increases its polarization to about 95%.
Before the sample is installed, four nylon thumb screws on the laser mount are used to aim the laser beam along the central axis of the solenoid.

The entire laser mount is removable so that an experimenter could use other light sources to study the frequency dependence of Faraday rotation. If any other sources are used, however, it is important that the intensity be stable. Small modulations in the frequency will not be as important.

The Solenoid
The solenoid is a 15 cm coil of #18 double insulated wire with DC resistance of 2.6 ohms. The approximate calibration at its center is:

B = (11.1mT/A) I

where I is in amperes and B is in millitesla.

The magnetic field does vary along the axis of the solenoid. Such variation may be significant for certain samples, particularly those which extend outside the coils. We recommend that the students measure the axial magnetic field profile using TeachSpin’s Hall Effect Probe HE1-A , or other equivalent field measuring apparatus.

The maximum continuous current through the unit is 3 amperes. For times of the order of 30 seconds, however, 10 amperes can be used without damaging the solenoid or its supports.

Since Faraday rotation measurements can easily be performed in 10-15 seconds by a student familiar with the equipment, it is possible to use these larger solenoid currents and thus obtain larger rotations.

The Analyzer Polaroid
The unit is equipped with a rotatable Polaroid film in a calibrated mount. The decal is marked in 5° increments. This limits the accuracy of an angular measurement to about 2°.

The Detector
The detector is simply a photodiode connected in series to one of three resistors; 10K, 3K, 1K. The photodiode is a current source and is a linear photonic detector, as long as the voltage across it is less than about 0.3 volt. Saturation begins to occur when this bias voltage appears across the diode. This makes the detector nonlinear. Varying the load resistor keeps the bias voltage below the 0.3 volt value

The Sample
FR1-A comes with one sample, a 10 cm long SF-59 glass rod with a diameter of 5 mm.
The sample is easily removed so that the optics can be aligned.

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