Changing crystal plane spacing changes the checked Bragg path budget. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The ray angle stays fixed across the scan
Every row uses the same 3 by 4 by 5 ray triangle, so the sine factor stays 3/5. Only the plane spacing changes.
sinθ=53
Spacing changes the extra path
The path difference is two times spacing times the same sine factor. The first-order wavelength follows that path exactly.
d5m10m15mΔ6m12m18mλ6m12m18m
The first rendered row closes the path budget
For the rendered row, spacing 5 meters gives path difference 6 meters and first-order wavelength 6 meters.