Diffraction of Light by Ultrasonic Waves, Oblique Incidence and Sound Intensity

Abstract

THE experimental results reported in a previous communication¹ confirm the existence of several maxima for the second- and the third-order diffraction lines at oblique incidence and at low sound intensities, when the sound wave-length is small as expected by the closed intensity expressions of Aggarwal². We have now observed for this small sound wave-length that, when the sound intensity is slowly increased, the number of these maxima diminishes. Further, the emphasis appears to shift towards the first Bragg angle, instead of the diffraction order attaining the maximum intensity at its respective Bragg reflexion angle. The secondary maxima for the second- and third-order diffraction lines at the Bragg angles corresponding to the higher orders slowly disappear, until the maximum intensity occurs only at the Bragg angle corresponding to the first order.