This item can only be shipped to schools, museums and science centers
Accurately measure Planck’s constant with this easy-to-use, compact apparatus. Unit contains an enclosed vacuum cesium (Cs) photocell, attachment for illuminating light sources, a high stability power supply and a nanoammeter. LCD displays showstopping voltage and photocurrent values. Light from five interchangeable, narrow-spectrum LEDs are incident upon the photocell via enclosed fiber optic cables. The LED cables plug directly into the photocell enclosure to minimize extraneous, ambient light sources. The maximum energy of photons from the LEDs is measured by determining the stopping voltage of the photocurrent, corresponding to the maximum wavelength of each LED. The energies and wavelengths of the LEDs are combined to calculate the value of Planck’s constant through graphical or analytical methods. The work function of the Cs photocell can also be estimated.