A solid with Face Centred Cubic (FCC) structure is probed by x-rays of wavelength 0.2 nm. For the crystallographic plane given by (2, 0, 0) a first order diffraction peak is observed for a Bragg angle of 30°. The unit cell size is -
1
0.2 nm
2
0.4 nm
3
0.1 nm
4
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