Diffraction grating

Four "Animated figure" models that help students understand diffraction gratings in stationary and Czerny-Turner mountings. There are three variations of this model:

Grat1 is a stationary grating with incident white light, pictured above. Eight colors of diffracted light shown in the first order only, plus the zeroth order reflection shown as a gray line. The colors of the diffracted beams roughly match the wavelengths of those beams. Students can change the angle of the incident beam and the grating ruling density. Download link: Grat1.WKZ
Grat2 is a stationary grating with incident white light, used to demonstrate the relationship between the first and second orders of diffraction. Six visible colors of diffracted light shown in the first and second orders, plus the zeroth order reflection shown as a gray line. The colors of the diffracted beams roughly match the wavelengths of those beams. Students can change the angle of the incident beam and the grating ruling density. Download link: grat2.wkz
Grating is a stationary grating with monochromatic incident light. Diffraction in the zeroth, first, and second orders are shown. The diffracted beams are shown in shades or gray and patterns; no use of color is made. Students can change the angle of incidence, the wavelength of the incident light beam, and the grating ruling density. Download links: Grating.wkz; Grating.hqx
CzernyTurner is a rotating grating in a Czerny-Turner mounting. Diffraction in the zeroth, first, and second orders are shown. The diffracted beams are shown in shades or gray and patterns; no use of color is made. Students can change the angle of rotation of the grating, the angle between the incident beam and observed diffracted beans, the wavelength of the incident light beam, and the grating ruling density. Download links: CzernyTurner.wkz; CzernyTurner.hqx

These models can be operated using only the mouse-activitated on-screen sliders and radio buttons, useful when used in a lecture-demonstration environment with a computer video projection system, in a darkened room, where it is difficult to use the keyboard data entry .
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Mathematical basis

Inputs:
(All angles measured from the perpendicular to the grating surface.)
Angle of incidence = alpha, degrees, changed by typing into entry table or by slider
Ruling density = R, lines/mm, changed by typing into entry table or by radio buttons

Calculated quantities:
Groove spacing = d, 1000000/R (displayed in nm in table).
alphar = alpha/(360/(2*pi()))
Angle of diffraction = asin(order*wavelength/d-sin(alphar))