When light of different known frequencies falls on the cell of this apparatus, electrons with a range of energies are liberated from the metal cathode. Planck's constant, h, is found from the variation of the measured maximum energy with the frequency of light used.

The small photocurrents are amplified to measurable levels by the built-in amplifier, which is specific to the ranges of this experiment. There is no additional external power supply required. A controlling potentiometer dial is provided to apply the necessary voltage to the photocell. You don't have to worry about stray light, because the photocell is also contained in the apparatus' box.

Four light filters are included on a dial window to select the frequency of light that hits the photocell. You'll need to supply a mercury lamp for a light source. Simply connect a voltmeter and a microammeter capable of 0.1mA resolution to the provided terminals on the apparatus for measurements. Adjust the stopping voltage downward for each frequency selected to obtain an ammeter measurement of the characteristic current emitted through the photocell.

Specifications:

• Photoelectric Tube: Ag-Cs
• Power Supply Input: AC110V-60Hz
• Dimensions: 27cm x 13cm x 15cm

Filters:

Designation:	UV-39	V-Y43	V-054	V-058
Frequency (Hz)*:	7.4 x 1014	6.9 x 1014	5.5 x 1014	5.2 x 1014
Thickness:	3.15mm	3.80mm	3.45mm	3.98mm