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## Homework Statement

The unit cell in a cubic crystal is 2.74Å. Determine the Bragg angle for reflections from the planes (200), (212) and (-112). [sorry i dunno how to put a bar on top of the numbers] if the x-ray wavelength used is 1.54Å

## Homework Equations

Given Bragg's condition as

*2d sinθ = nλ*

and

*d = 2π /|*

__G__|where

*according to Laue condition.*

__G__= h__a__* + k__b__* + l__c__*there's also

*d = a /√(h^2 + k^2 + l^2 )*

where a is the edge length.

## The Attempt at a Solution

Since d is the distance between planes in atomic lattice, I guess it meant the distance of (200), (212) and (-112) to the origin. So I calculated is by finding the magnitude of G. Then i got confused by the two d equations. Should I use 2π or a to divide with |

__G__| to find the Bragg angle? I thought a is more logical, but the 2π /|

__G__|[/I] is making me confused. What are the difference between them?

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