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Planck's constant
The aim of this experiment is for students to be able to determine for themselves the threshold voltage needed to activate a range of LEDs of different colours. From these values, combined with a knowledge of the wavelengths of each LED, students can plot a graph to determine a value for Planck’s constant. The teaching materials also encourage students to think about the particulate nature of light: individual photons are given off that correspond to specific jumps in electron energy shells.
Students can build the apparatus themselves, if teachers decide they have time to fit it into their schemes of learning.
More detailed guidance on how to use these teaching resources can be found in the overview document.
Building Planck's constant
In this video we build a simple circuit that can be used to slowly increase the potential difference to an LED.
Measuring Planck's constant
Using a simple circuit which can control the potential difference across an LED so that we can determine a value for Planck's constant.
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