Experiment 12: CD Diffraction

The purpose of this lab was to calculate the grove spacing on a CD and DVD.

Procedure:

We shine a laser through a hole in a piece of cardboard to a CD or DVD.  We then measure the reflected interference maxima at a certain distance.

Data:

The equation used was sinθ = mλ/a. Then sine is replaced for values of length and slit distance, and solve the equation for a, the grove spacing.  We get:

λ is the lasers wavelength, and m is the order.

	λ(nm)	m	y(cm)	L(cm)	a(nm)
CD	632	1	4±0.1	10	1702±51
DVD	632	1	15.1±0.1	10	752±61

Analysis:

The manufacturer’s standard value is 1600 nm for a CD.  We got 1702±51nm which does not exactly fall into our error range, but it is close.  The DVD has a much smaller slit spacing, which we calculated it to be 752±61nm.