---
title: See the Air Move with This Cool Device — HIGH T3CH
url: https://hight3ch.com/see-the-air-move-with-this-cool-device/
date: 2014-11-25
---

# See the Air Move with This Cool Device

Demonstration of an optical technique that allows us to see small changes in the index of refraction in air. A point source of light is reflected from a concave mirror and focused onto the edge of a razor blade, which is mounted in front of the camera. Light refracted near the mirror and intercepted by the blade gives the illusion of a shadow.