PURPOSE: White light Schlieren imaging of a candle flame.
DESCRIPTION: The lenses are positioned so that the condenser lens focuses the beam at the first sharp edge, which is at the focal point of L1, and the second edge is at the focal point of L2, with parallel light in between. The candle is positi oned so that L2 forms an image of the candle on the screen. The two edges are then symmetrically moved into the beam such that the direct light is cut off, leaving only the light deflected by the candle flame on the screen. In the picture the Schlieren image of the flame can be seen in the central bright spot with the direct image of part of the candle flame above (actually below, before being inverted by the lens).
REFERENCES: (PIRA unknown.) See Demonstration Reference File for further information and references.
EQUIPMENT: Bright point source with condenser lens, adjustable sharp edge on vertical cross carriage adjustor, 30cm focal length achromatic convex lens, candle, 20cm focal length achromatic convex lens, adjustable sharp edge on vertical cross ca rriage adjustor, and screen, on optical rail assembly.
SETUP TIME: 20 min.
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