HI, I am practicing some exam questions to get ready for a repeat, below is the question I am having trouble with.
"The lattice constants of KCl and KBr are 6.29 angstroms, and 6.59 angstroms, respectively.
What would be the first two observed Bragg diffraction angles in each case , if the wavelength of X-rays was 1.932 angstroms? (assume Debye-Scherrer method is used.)
Here, Braggs law is relevant,
The Attempt at a Solution
Braggs law can be rearranged to give θ = sin^-1(nλ/2dhkl).
the Questions asks for the first two angles for each case, so n=1 and n=2 for the first and second angle.
my two problems, are, how can I use α, the lattice constant to get dhkl?
Since the two Crystals are both FCC, the lattice parameters are a=b=c, and α=β=γ,
dhkl =[1/a^2 + ( h^2 +k^2 + l^2)]^-1/2
I haven't been given any miller indices for h,k &l, so do I assume some, or just use α as dhkl?
Also, will the angles be in units of radians or degrees?
Any help or push in the right direction will be much appreciated.