A CD (or gramophone record) as a grating
Students observe the spectrum produced when light falls obliquely on a CD.
Apparatus and materials
CD or gramophone record
Health & Safety and Technical notes
Students might like to look at the grating spectra formed by reflection when light falls obliquely on a CD.
The rulings are too coarse to be useful at direct incidence. The observer must take an oblique view.
If it is a gramophone record, you can calculate the grating spacing. Use a ruler to measure the part of the radius of the grating used. Play it and count the corresponding number of turns.
Measuring the grating spacing of a CD will be more challenging.
Alternatively, use a known wavelength of light to estimate the grating spacing of a CD.
This experiment was safety-checked in February 2006