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Bragg diffraction

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Mountain View


Introduction

Procedure

Results & analysis

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

Figure 1. Measurement of Bragg difraction

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.

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