Demonstrating diffraction using laser light - for classroom use 

In this short video, from the Institute of Physics and the National STEM Learning Centre and Network (www.stem.org.uk/), Michael de Podesta explains how a laser can be used to show the diffraction and interference of light. Using a laser pen in the classroom, the wave nature of light is demonstrated as a thin wire is used to generate an easily-seen interference pattern. Two versions of the video are available. One is suitable for teachers and fully explains the demonstration and how the interference pattern is produced. This one is aimed at students and could be used in place of the demonstration.