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Planck's Constant Apparatus

(ships from manufacturer, est arrival 5/1/23)


Advanced physics items are drop shipped. These products are built to order. Carolina does not hold stock. Please allow 90 days to receive your item from the time you place your order. This is the industry standard for this type of equipment.

Using Planck's Constant Apparatus, the classic experiment to demonstrate outer photoelectric effect and measure Planck's constant can be performed.

Learn the concept of quantization of light. Highly accurate under normal lab conditions, this apparatus includes 5 precision plug-in LED modules, a vacuum photocell, an integrated voltmeter and nanoammeter, and control circuitry, all in a compact, lightweight unit. Photocurrent range is 10-9 to 10-12 A. The picoampere amplifier unit provides a highly stable, well-shielded current amplifier and a very precise, stable source of the variable reverse voltage. The stabilized LED supply and amplifier routinely allow Planck's constant to be determined within 3%. Powered by a 50-W high-voltage mercury lamp, this lamp and a set of matching narrow-band interference filters rigorously exclude all light except the wavelength being measured.

The included instruction manual contains theoretical background, sample activities, and sample data. Recommended for advanced or college-level physics students. V-I graphs of the phototube output can also be plotted with an x-y recorder (not included) connected through the outlets on the back panel.

Picoampere Amplifier and Control Unit

Imposes a highly stable DC voltage of -2.000 to +2.000 V onto the photocell. The voltage is adjusted by a 10-turn potentiometer. The unit has a digital voltmeter and analog ammeter.

Voltmeter: 3-1/2 digit LED display
Current Measurement Range: 10-9 to 10-12 A in 5 steps
Zero Drift: < ±2% at 10-3 A over 8 hr (60 min after instrument is turned on)
Phototube Voltage Supply: -2.000 to +2.000 V, precisely adjustable, with error < 0.1%

Mercury Light Source (ballast is mounted in the base)
Housing has a window on the side, with a fixed diaphragm.
Lamp: GGQ-50-W high-voltage mercury vapor lamp
Spectral Range: 320.3 to 872.0 nm
Usable Spectral Lines: 365.0, 404.7, 435.8, 491.6, 546.1, and 577.0 nm

Interference Filters, Type ZG II, Medium Film
Type: Narrow-band, multi-layer film
Bandwidth: <50 nm
Wavelengths Supplied: 365.0, 404.7, 435.8, 546.1, and 577.0 nm
Diameter: 30 mm

Phototube, Vacuum, Type GD-2 (mounted inside photocell unit)
Anode: Nickel ring, 25 mm diam
Cathode: Ag-O-K
Window: Boron-silicon glass
Spectral Response Range: 30 to 700 nm
Peak Wavelength: 350 nm, ±20 nm
Minimum Cathode Sensitivity: 1 mA/lm
Dark Current: ~10-12 A
Ratio of Reverse Current to Positive Saturation Current: <0.5%

Condenser lens (installed in the light entry tube located on the front of the photocell unit)
Accuracy: < 5% with respect to the accepted value (h=6.62619 x 10-34 Js)
Power Supply: 110-V AC, 60 Hz
Dimensions: 280 x 120 x 160 mm
Weight: 1 kg (2-2/10 lb)


What’s Included:
  • 1 Picoampere Amplifier and Control Unit
  • 1 Lamp, Mercury, High Voltage, 50 W
  • 5 Interference Filters
  • 1 Phototube, Vacuum, GD-2
  • 1 Lens, Condenser (adjustable)
  • 1 Instructions
Needed But Not Included:
  • 1 Hair Dryer
  • 1 X-Y Recorder (optional)
Return Policy:

If for any reason you are not satisfied with this item, it is eligible for a return, exchange, refund, or credit up to 180 days from date of purchase. Restrictions may apply. Returns & Exchanges Policy.


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