If you are not familiar with Schlieren photography, you are not alone. It is a photography technique that allows the differing densities of gases to be photographed. Now Dr. Gary Settles, an engineering professor at At Pennsylvania State University and Dr. Julian Tang, a virus expert from Singapore have used the technique to capture, for the first time, the gas dynamics of a cough.

The process involves a small, bright light source, precisely placed lenses, a curved mirror, a razor blade that blocks part of the light beam and other tools that make it possible to see and photograph disturbances in the air.

The justification for the project as provided by Settles:

The next thing is, you get a couple of people in front of the mirror talking, or one coughs on another, and you see how the air flow moves, how people infect one another. Or you look at how coughing can spread airborne infection in a hospital. This is really a suggestion for how we might study all that. The techniques used in wind tunnels can be used to study human diseases.

For a few more images check out the source article at IHT.

Figure Legends

Title:Settle’s now famous Schlieren image of a cough.
Fig1:A bomb blast designed to simulate a terrorist attempt to bring down a Philippine Airlines flight.
Fig2:The shockwave as an AK-47 is fired.
Fig3:Gaseous discharge as a revolver is fired shows how gunpowder residue reaches the hand of a shooter.
Fig4:A humble hairdryer makes for a spectacular effect.
Figures 1-4 are in the order that they appear from left to right.
[IHT]