Optics > Geometric Optics > Refraction DCS# 6A40.60
SCHLIEREN OPTICAL SYSTEM

APPARATUS
long focal length concave mirror
 202-10-A
white LED with pinhole mask
 202-21-F5
rainbow filters
 202-21-F5
DC power supply for the LED
 202-08-D
razor blade, mounted
 202-21-C5
video or document camera
 202-09-C4
soldering iron, candle, or other heat source
 202-02-C1

DESCRIPTION
A concave mirror is used to image a point source of light on a razor's edge.  Any nonuniformities in the refractive index of the air in the light path can deflect the light so that it reaches the camera and appears as a bright region or is blocked by the blade and appears dark.  Convection currents from your hand or a candle cause variations in the refractive index of the air which appear as variations in light intensity.

NOTES