1. Introduction

The photoelectric effect and its explanations were important foundations for modern physics. It was for his explanation of the photoelectric effect that Einstein received the Nobel prize. In this set of experiments you will demonstrate the quantum behavior of light and measure Planck's constant. There are two methods for measuring Planck's constant in this lab. The first is the traditional method as explained in elementary text books. Light of varying wavelengths is incident on a metal surface and the kinetic energy of the emitted electrons are measured. In the second method the process is reversed. Light Emitting Diodes (LED) are used to inject electrons into a PN junction where they recombine with holes and emit light.

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