Bragg Angles + Thermal Expansion

[exzacklyright]

Homework Statement

A crystal is heated from 0 to 100 degrees celcius, its lattice parameter 'a' increases by 0.17% due to thermal expansion. if we observe an x-ray reflection at a bragg angle theta= 19.3 degrees at 0 degrees celcius, by how much will theta change when the sample is heated to 100 degrees C. (don't need to know wavelength or d to solve)

Homework Equations

2dsin(theta) = n\lambda

The Attempt at a Solution

Tried using 1 for d. and just seeing how much it'd change but it didn't come out right.

 

[Spinnor]

Should it be d_1*sin(theta_1) = d_2*sin(theta_2) ?

 

[exzacklyright]

Should it be d_1*sin(theta_1) = d_2*sin(theta_2) ?

well all we're given is density 1 and theta 1. we don't even know density2 or theta2