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# Braggs Law and Equation watch

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1. n*lambda = d*sin(theta)

Now I am aware n = order and I guess this means order of maxima formed ?

During X Ray Crystallography how is the value for n determined ?

Also, what is theta ? The angle at which the X Rays are fired at the crystal ? Can it be determined from the angle at which the X Ray source is kept at ?
2. Monday morning tutorial?
3. (Original post by Computerised)
Monday morning tutorial?
I'm doing my A Levels.... This is just further reading I'm doing.
4. (Original post by Ari Ben Canaan)
n*lambda = d*sin(theta)

Now I am aware n = order and I guess this means order of maxima formed ?

During X Ray Crystallography how is the value for n determined ?

Also, what is theta ? The angle at which the X Rays are fired at the crystal ? Can it be determined from the angle at which the X Ray source is kept at ?
The formula for the Bragg Law is

Theta is the angle the X rays make to the plane of the crystal.
n is determined in the same way it would be for a diffraction grating.
n = 1 for the 1st bright (=constructive interference) spot observed.
That is, the lowest value of theta. n = 2 for the next bright spot for the next (higher) value of theta.
5. (Original post by Stonebridge)
The formula for the Bragg Law is

Theta is the angle incident the X rays make to the plane of the crystal.
n is determined in the same way it would be for a diffraction grating.
n = 1 for the 1st bright (=constructive interference) spot observed.
That is, the lowest value of theta. n = 2 for the next bright spot for the next (higher) value of theta.
But often you'll notice the results of an x ray crystallography analysis have spots all over the place.... not in the nice pattern we see with a diffraction grating.

How do the determine that a certain spot correspnds to the nth order ?
6. (Original post by Ari Ben Canaan)
But often you'll notice the results of an x ray crystallography analysis have spots all over the place.... not in the nice pattern we see with a diffraction grating.

How do the determine that a certain spot correspnds to the nth order ?
As always at A Level (is X-ray diffraction in your syllabus?) things are kept simple in the initial stages. Bragg diffraction as described here is the simplest (one dimensional) case where you have one simple crystal structure that has nice parallel, uniformly spaced planes of atoms.
This diffraction pattern is the simplest, one dimensional, pattern possible.
The pictures you have probably seen with many spots are 2d and 3d patterns where the X rays are scattered through many angles by many different planes of atoms making up the crystal. The process of analysing those patterns of spots is very complex and done via computation, where the program takes the pattern of dots observed and works backwards to calculate the arrangement of atoms that produced it.
However, underlying that complexity is still the fundamental idea that the X rays are undergoing constructive interference when the Bragg condition is satisfied, and each dot on the screen is the result of this.
7. (Original post by Stonebridge)
As always at A Level (is X-ray diffraction in your syllabus?) things are kept simple in the initial stages. Bragg diffraction as described here is the simplest (one dimensional) case where you have one simple crystal structure that has nice parallel, uniformly spaced planes of atoms.
This diffraction pattern is the simplest, one dimensional, pattern possible.
The pictures you have probably seen with many spots are 2d and 3d patterns where the X rays are scattered through many angles by many different planes of atoms making up the crystal. The process of analysing those patterns of spots is very complex and done via computation, where the program takes the pattern of dots observed and works backwards to calculate the arrangement of atoms that produced it.
However, underlying that complexity is still the fundamental idea that the X rays are undergoing constructive interference when the Bragg condition is satisfied, and each dot on the screen is the result of this.
Yes and no. We are required to 'be aware' (whatever that means) of X-Ray Diffraction in my syllabus.

Oh, alright, that's what I wanted to know basically.

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Updated: November 28, 2011
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