TEL 310 Photoelectric Effect

This apparatus allows the student to repeat the experiment that served to establish the quantum theory of radiation. It effectively demonstrates that the energy of a photoelectron depends on the wavelength of the impinging radiation and not its intensity.

In this experiment, the photocathode is irradiated by a source of monochromatic radiation and a potential applied to the tube so that it opposes the energy of the emitted photoelectrons. The voltage required to just stop the current flow is proportional to the energy of the photoelectron. Plotting the stopping potential as a function of the reciprocal of the wavelength of the radiation gives a straight line plot,the slope of which can be used to calculate Planck’s constant. Typical values for this experiment are shown in the graph.

The measurement of very small photocurrent is required for accurate results; therefore, the amplifier is located only a couple of centimeters from the photodiode. This avoids the introduction of extraneous voltages and achieves a minimum detectable photocurrent of the order of 5 x 10-10A.

The apparatus includes three filters to provide spectral separation. The use of the Small Mercury Arc monochromatic light source, TEL-1819 is recommended. A tungsten lamp can be used, instead of the recommended light source, although the results are not as good as with a monochromatic source.

Mounted inside the amplifier case.
Amplifier Mounted within the case. Consists of an FET input Op Amp followed by a second Op Amp driving the panel meter. Power supplies are internal.
Amplifier Gain 3 x 107
Minimum Current Sensitivity 5 x 1010Spectral Separation Provided by red, green and blue filters. Best results are obtained with monochromatic sources such as a mercury arc and a He-Ne laser.
Dimensions 9w x 17l x 10h cm (3.5 x 6.7 x 3.9 in).
TEL 310$1050.00

TEL-310LS2 Photoelectric Effect with light source and stand $1,711.00

Monochromatic Light Source
The small 7-watt low-pressure mercury arc is a perfect source of monochromatic radiation for the TEL-310 Photoelectric Effect. It comes with its own power supply and is shown mounted on a bench carrier, which is available separately. A stand to hold the lamp in position when using it with the Photoelectric Effect experiment is included (not pictured). The envelope is quartz and comes equipped with a stray light shield.

TEL-ES1819 $754.00