An intensity distribution derived from this approximation explains the appearance of Airy disks. For 10 points each:
[10m] Name this approximation that is valid under a namesake “condition” which states that the square of the largest width is significantly less than lambda times the distance between two planes.
ANSWER: Fraunhofer diffraction equation [or far-field diffraction; prompt on Fraunhofer or far-field by asking “what physical phenomenon does that approximate?”]
[10h] This theorem is used to calculate the Fraunhofer diffraction from multiple identical apertures. This theorem is derived by viewing the 2D convolution of aperture functions and corresponding delta functions as a Fourier transform.
ANSWER: array theorem
[10e] The array theorem can be applied to describe diffraction from these devices that consist of arrays of equally spaced identical slits. CD tracks act as these optical devices.
ANSWER: diffraction gratings [or transmission gratings]
<Geoffrey Wu, Physics>