Bragg diffraction

Results & analysis

The results of the measurement are shown in Figure 1 (below; note the error bars!).

We can identify clearly six peaks at $12^{\circ}$, $20^{\circ}$, $24^{\circ}$, $31^{\circ}$, $47^{\circ}$ and $59^{\circ}$. Considering that the wavelength of the source used to measure the diffraction is $\lambda=2.85\,\mathrm{cm}$, we use Bragg's law to obtain the following values for the interplane distance $d$:

Peak position ($^{\circ}$)	Diffraction order ($n$)	$d$
12	1	(6.12 $\pm$ 0.25)
20	1	(3.77 $\pm$ 0.09)
24	1	(3.17 $\pm$ 0.06)
31	1	(2.50 $\pm$ 0.03)
47	2	(3.53 $\pm$ 0.03)
59	2	(3.01 $\pm$ 0.02)

The actual separation between planes is $(3.80 \pm 0.05)\,\mathrm{cm}$, from which we can conclude that the peaks at 20$^{\circ}$ and at 47$^{\circ}$ correspond to the first and second diffraction orders of the planes. The other peaks, therefore, must be due to reflections with other planes of the crystal.

Useful links

• The manual to set up the experiment is Media:Microwave-Optics.pdf here.