- A picture or image in which steep density gradients in the flow about a body are made visible, the body itself being presented in silhouette.
- The optical method or technique by which this is done. A shadowgraph differs from a schlieren photograph in that the schlieren method depends on the first derivative of the refractive index while the shadow method depends on the second derivative. Interference measurements give the refractive index directly.
See also: Density, Schlieren.
Subjects: Optics Physics