Quick Answer: Plancks Constant Apparatus is a Planck's Constant Unit with a photo emissive caesium antimony cathode that gives a reasonable order of magnitude value for h and demonstrates the photoelectric effect using a backing potential difference.
Backing potential difference from an internal PP3 (6F22)-type cell, adjustable to reduce the anode current to zero
Colour filters placed over the cell select different light frequencies
A plot of V against f gives a reasonable straight line with gradient h/e
Demonstrates the photoelectric effect
Technical Specifications
Specification
Value
Cathode
Caesium antimony, photo emissive
Spectral response
185-650 nm
Backing voltage source
Internal PP3 (6F22)-type cell
About This Product
Light of frequency f releases electrons from the cathode, and the backing potential difference is adjusted to the value V at which the anode current is just reduced to zero. Repeating this with each colour filter over the cell gives V for several frequencies, and the gradient of V against f gives h/e. Export supply of the Plancks Constant Apparatus can be arranged to laboratories and schools in Democratic Republic of the Congo, Qatar, Kiribati, Iceland, Cameroon and Panama.
Frequently Asked Questions
Q1. What else is needed to operate it? A Spacesaver Picoammeter, a PP3 battery, an Easy-Read Meter, a set of six colour filters, a set of 3 narrow band filters and a 20V d.c. attachment.
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