Track pitch of a CD and DVD

Diffraction gratings come as either transmission gratings or reflection gratings. A CD or DVD has a shiny surface and a very narrow track pitch and can hence be used as a reflection grating.
In this video, I use a common red laser pointer. The wavelength of its light is determined with a 600 lines/mm transmission grating. Once the wavelength is known, the track pitch of the CD and DVD can be investigated by looking at the diffraction pattern bouncing off its surface. I measure the distance between the right and left first-order maximum to increase measuring accuracy.
The literature gives a track pitch of 1.6 microns for the CD and about 0.74 microns for the DVD. With the values measured in the experiment, this can be reproduced quite well.
Contents:
0:00 Preparations
2:49 Alignment of the beam
3:48 Diffraction pattern and measurement
5:39 Switching to DVD
7:10 Measurement for the DVD
8:08 Wavelength of the laser pointer
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Some theoretical background:
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This experiment is very similar to the one shown in the video "diffraction grating". It is based on the same principles, however, this time a reflection grating instead of a transmission grating is used. A CD and a DVD are cheap alternatives to professional reflection gratings.
A laser light beam hitting the surface of the CD perpendicularly is mainly reflected straight back (maximum of zeroth order). However, light waves that are not reflected straight back can interfere with each other to produce maxima of higher order. In this video the distance between the two maxima of first order is measured, allowing us to derive the track pitch.
Generally speaking, the shape and size of the diffraction pattern can be used to get a clue about the diffracting object, an object which might be too small to be measured with traditional methods.