Two X-ray diffraction angles 8.9 and 18.0 are measured for the first two orders from a particular crystal. Explain why from these two pieces of information you cannot determine either crystal spacing or the wave length of the X-rays.
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The diffraction angle depends on the ratio wavelength (L) to spacing (d). So you can only find the ratio, not the actual values of spacing or wavelength, from the angle.
You can see this if you look at the standard formula, which can be rearranged as
L/d = 2sin(theta)/order
You can see this if you look at the standard formula, which can be rearranged as
L/d = 2sin(theta)/order