Optical Reflection at Grazing Incidence from a Shock Front

The reflection of light at grazing incidence from a shock wave at Mach No. 1.94 in air at atmospheric pressure is measured. It is found that the reflection coefficient is equal to that calculated when second-order effects are included. From the variation of the reflectivity across the front it is found that the shock has a curvature of 5.4±0.4 m, a tilt of less than ±⅕, and distortion amplitude of less than 3×10−3 cm.