A neutron beam of energy E scatters from atoms on a surface with a spacing d = 0.1nm. The first maximum of intensity in the reflected beam occurs at θ = 30°. What is the kinetic energy E of the beam in eV?
Here, d=0.1nm,θ=30∘,n=1d=0.1nm,θ=30∘,n=1. According to Bragg's law 2dsinθ=nλor2×0.1×sin30∘=1×λorλ=0.1nm=10−10m2dsinθ=nλor2×0.1×sin30∘=1×λorλ=0.1nm=10-10m p=hλ=6.62×10−3410−10=6.62×10−24kgms−1p=hλ=6.62×10-3410-10=6.62×10-24kgms-1 KE=12p2m=12×(6.62×10−24)21.67×10−27J=12(6.62×10−24)2(1.67×10−27)×(1.6×10−19)eV=0.082eV