## Description

Grades 9–12. In 3 experiments, students determine the wavelength of 4 LED colors and construct a circuit to find the threshold voltage of the LEDs. This is used to calculate frequency and energy, and to generate a mathematical model for Planck’s constant. Activities are designed for 4 groups working in 4 student teams. This kit is designed to integrate into a larger unit of lessons addressing wave mechanics, electricity, magnetism, and electromagnetism.

Time Requirement: 90 minutes

Using Mathematics and Computational Thinking

Systems and System Models

Electromagnetic Radiation

Take a smartphone selfie, walk through an automatic door, or turn on your television with a remote, and you’re using light sensors based on the photoelectric effect.

In this comprehensive kit students:

Investigate light sensors and the photelectric effect

Learn how light-emitting diodes (LEDs) and transistors function

Students establish relationships among light frequency, wavelength, and energy for LEDs while collecting data to calculate Planck’s constant.

Build circuits to determine Planck’s constant

Investigate the wave and particle models of light as students calculate threshold voltages to turn on LEDs (photoelectric effect) and calculate wavelength using a diffraction grating. The photoelectric effect and the discrete nature of quantum mechanics are addressed, laying the foundation for this lab.