# Bragg condition ambiguity

1. Mar 5, 2009

### thefireman

Hello, I have a quick question regarding the bragg condition.

I know that it is most often stated as $$2dSin \theta=n\lambda$$

But I have come across a case (Kittel chp9 pg 255, where it is written as ($$\vec{k}$$+$$\vec{G}$$)$$^{2} = k$$

I cannot really see how the vectorial case is the same as the simpler former one.
Could someone elucidate?

Thanks

2. Mar 5, 2009

3. Mar 5, 2009

### nasu

Or look in the same book (Kittel -Chapter 2) where the equivalence of the two formulas is discussed explicitly.

4. Mar 5, 2009

good call!