Answer : The correct answer is : 29.34 °
The spacing between layers , incident angle and wavelength is described by Bragg's Law which states :
nλ = 2d sin∅
Where , n = an inetger
λ = wavelength of the x-ray
d = spacing of crystal layers ( path difference )
∅ = is incident angle
Given : = d = 157 pm λ= 154 pm n=1
Plugging values in formula => 1 * 154 pm = 2 * 157 pm * sin∅
154 pm = 314 pm * sin∅
Dividing 314 pm on both side .
154 pm/ 314pm = 314pm/314pm * sin∅
0.490 = sin∅
∅ = sin^-1 0.490
∅= 29.34 °
