Simple, safe and quick-to-operate, compact apparatus with integrated photocell as well as a voltmeter and nano-ammeter for determining Planck's constant and the work done in emitting an electron using the stopping potential method. Five light emitting diodes (LEDs) of known mean wavelengths act as light sources of differing frequencies. The intensity of the light emitted by them can be varied from 0 to 100%.

Specifications:

• Wavelengths: 472 nm, 505 nm, 525 nm, 588 nm, 611 nm
• Dimensions: 280x150x130 mm³
• Weight: 1.3 kg approx.
  

• 1 Basic apparatus with photocell, voltmeter, nano-ammeter, and power supply for light sources
• 5 LEDs in casings with connector leads
• 1 Plug-in power supply 12 V AC