Schlieren Effect Experimentation

Schlieren Effect

Today we attempted to experiment with the Schlieren Effect. This is a means of "visualising air density due to small changes in the index of refraction in air are made visible by Schlieren Optics. With a video camera and monitor, we can see warm convection currents rising from your hand or, alternatively, cold air sinking from a glass of ice water. Gases other than air can also be seen with this technique."

"The collimated light is focused with a converging optical element (usually a lens or curved mirror), and a knife edge is placed at the focal point, positioned to block about half the light. In flow of uniform density this will simply make the photograph half as bright. However, in flow with density variations the distorted beam focuses imperfectly, and parts that have been focused in an area covered by the knife edge are blocked. The result is a set of lighter and darker patches corresponding to positive and negative fluid density gradients"

Expected results:

Outcome:

Unfortunately when attempting to carry out the experiment, we could not achieve the above results. Upon reflection, we figured that this was likely due to the household concave mirror that we were using not being of optical industrial grade.