The Reflection of theKαLine of Carbon From Glass

A vacuum spectrograph was constructed in which a beam of monochromatic radiation in the extremely soft x-ray region could be isolated by means of a ruled grating and then reflected from a mirror. This mirror could be rotated and the intensities of the reflected rays corresponding to various glancing angles of incidence could be compared by a photographic method. Using a glass surface and the $K\alpha$ line of carbon (wave-length = 44.6A) measurements of reflected intensity were made for glancing angles of incidence between 1° and 8°. At 8° the reflected intensity was found to be less than 4 percent of the intensity at 1°. However the curve relating intensity of reflection with glancing angle of incidence shows no abrupt change of slope, such as would occur in the case of hard x-rays. This indicates that absorption effects modify the intensity of the reflected ray sufficiently to obscure any sudden change at the critical angle in the case of the reflection from glass of wave-lengths as long or longer than 44.6A.