Bragg scattering angle for thermal neutrons in crystal

[getcarter]

I am really stuck on this problem. This entire section I have been teaching myself using the homework answers but I have no idea where to start. Thanks anyone.

Question:
A beam of thermal neutrons emerges from a nuclear reactor and is incident on a crystal as shown below. The beam is Bragg scattered from a crystal whose scattering planes are separated by 0.247nm. From the continuous energy spectrum of the beam we wish to select neutrons of energy 0.0105eV. Find the Bragg scattering angle that results in a scattered beam of this energy. Will other energies also be present in this scattered beam?
http://qaboard.cramster.com/answer-board/image/373f241a0a260e4f6fd216bbcb88754a.jpg

Homework Statement

d = 0.247 nm
E of neurons 0.0105ev

Homework Equations

http://earth.esa.int/applications/data_util/SARDOCS/_icons/c3_bragg.jpg

http://earth.esa.int/applications/data_util/SARDOCS/_icons/c3_brag_formula.jpg
http://earth.esa.int/applications/data_util/SARDOCS/_icons/c3_brag_formula1.jpg

The Attempt at a Solution

2dsin(tetha) = n(lamda)
from here sin(tetha) comes.

 

[phz]

Calculate the wave-length of the neutron through the de Broglie-relation. Then use the Bragg condition to identify the angle.