The angle of the first order diffraction

[cake_is_a_lie]

Homework Statement

What is the angle of the first order diffraction, m=1, when X-rays diffract from a crystal in which a spacing between atomic planes is 0,175nm? The 2nd diffraction, m=2, occurs at 45^o.

Homework Equations

Δr=2dcosθ_m=mλ
m+1/m = cos45/cosθ_m , because when the m increases the θ_m decreases.

The Attempt at a Solution

m+1/m = cos45/cosθ₁
θ₁ = 69^o.

What do you think? Just asking because I am not 100% sure.

 

[M Quack]

Last time I checked, Bragg's law was m lambda = 2 d sin(theta)...

Higher order reflections always occur at larger Bragg angles.

 

[cake_is_a_lie]

I my case it is cosθ_m. Yep, I think this should be the right answer because the angle is bigger than 45^o.