# Why is intensity decreasing for higher orders of Bragg (x-ray)diffraction?

Bragg diffraction for x-rays by a crystal structure is governed by

$$n\lambda=2dsin\theta ,$$

where $$n$$ is an integer and the diffraction order, $$\lambda$$ is the x-ray wavelength, $$d$$ the lattice spacing and $$\theta$$ the angle of incidence, taken from the horizontal.

I obtained the x-ray diffraction spectrum of NaCl, clearly showing all expected features, namely the first, second and third orders of the characteristic $$K_{\alpha,\beta}$$ peaks, enveloped by the bremsstrahlung spectrum.

The repeated peaks decrease in height and increase in spacing, with order - but why? I can explain the increase in spacing, but why do fewer x-rays interfere constructively at higher (steeper) angles of incidence? My suggestion is that this has something to do with the scattering mechanism (Thomson scattering) but works I have looked at are highly theoretical, and beyond my current scope. Is there a simple or heuristic way of looking at this?