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# Investigating Planck's Constant with LEDs

Planck’s constant (*h *= 6.626 × 10^{−34} J·s) is the most fundamental quantity in quantum physics. This classroom resource presents a simple lab activity that allows students to measure Planck’s constant and explore the quantum nature of light (i.e., photons), using light-emitting diodes (LEDs). It aims to make Planck’s constant and quantum physics more tangible and “real” to students.

The resource includes two versions of the lab. The first version is a structured investigation. Students follow instructions to build a simple circuit and make measurements that allow them to measure Planck’s constant. The second version is a guided inquiry activity. Students develop and test a mathematical model in which Planck’s constant is an important proportionality constant.

This is the new edition of our popular *Measuring Planck's Constant* resource. The new edition is currently available in English and French only.