The metal niobium crystallizes in a body centered cubic unit cell. ?

Question

The metal niobium crystallizes in a body centered cubic unit cell. When X-rays with λ = 0.8302 Å are used, the second-order Bragg reflection from a set of parallel planes in a(n) niobium crystal is observed at an angle θ = 14.57°. If the spacing between these planes corresponds to the unit cell length (d = a), calculate the edge length of the niobium unit cell. 

Answer 1

Bragg's law: 2 d sinθ = n λ

For second-order, n = 2:

2 d sinθ = 2 λ

d = λ / sinθ = 0.8302 / sin14.57° Å = 3.300 Å

The edge length of the niobium unit cell, a = d = 3.300 Å

Answer 2

did you try looking up bragg reflection?

https://www.britannica.com/science/Bragg-reflectio...

note the relationship between dsinθ and wavelength and "d" the spacing between the lines (this is your unit cell edge length)