Bragg Diffraction: Calculate 1st & 2nd Order Angles

In summary, the spacing between atomic planes in a crystal is 0.120 nm and 15.0 keV x rays are diffracted by this crystal. The angle of first-order diffraction can be calculated using the formula 2dcosΘ=mλ, which takes into account the angle between the crystal surface and the diffracted beams. This is different from the more commonly used formula, 2dsinΘ=mλ, which considers the angle between the normal and the diffracted beams. This is because Bragg diffraction is caused by reflection of X rays from the surface of the crystal, rather than transmission.
  • #1
Mohammed Shoaib
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The spacing between atomic planes in a crystal is 0.120 nm . 15.0 keV x rays are diffracted by this crystal What is the angle of first-order diffraction?What is the angle of second-order diffraction?My question is that the manual says to use 2dcosΘ=mλ instead of 2dsinΘ=mλ( bragg diffraction condition). Why?
 
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  • #2
Can you illustrate with a diagram?
 
  • #3
Mohammed Shoaib said:
The spacing between atomic planes in a crystal is 0.120 nm . 15.0 keV x rays are diffracted by this crystal What is the angle of first-order diffraction?What is the angle of second-order diffraction?My question is that the manual says to use 2dcosΘ=mλ instead of 2dsinΘ=mλ( bragg diffraction condition). Why?
With Bragg diffraction the angle used in the analysis is the angle between the crystal surface and the diffracted beams,...NOT the angle between the normal and the diffracted beams (you are probably more familiar with that one...Sin theta)
The diffraction is caused by reflection of X rays from the surface of the crystal not transmission (which is usually the case with light and transmission gratings)
 
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What is Bragg Diffraction and how does it work?

Bragg Diffraction is a phenomenon in which electromagnetic radiation, such as X-rays, is diffracted by a crystal lattice. This is due to the interference of the radiation with the regularly spaced atomic planes in the crystal. The diffracted waves constructively interfere at specific angles, known as Bragg angles, resulting in a diffraction pattern.

What is the formula for calculating the 1st and 2nd order Bragg angles?

The formula for calculating the 1st order Bragg angle is given by θ = arcsin(nλ / 2d), where θ is the angle of diffraction, n is the order of diffraction (1 for 1st order), λ is the wavelength of the radiation, and d is the distance between atomic planes in the crystal lattice. Similarly, the 2nd order Bragg angle can be calculated using θ = arcsin(2nλ / 2d).

What factors affect the Bragg angle?

The Bragg angle is affected by the wavelength of the radiation, the distance between atomic planes in the crystal, and the order of diffraction. It is also dependent on the type of crystal and its orientation, as well as the incident angle of the radiation.

What is the significance of the Bragg angle in diffraction experiments?

The Bragg angle is significant in diffraction experiments as it allows for the determination of the atomic structure of a crystal. By measuring the angles at which diffraction occurs, researchers can determine the distance between atomic planes and the arrangement of atoms in the crystal lattice, providing valuable information about the material's properties.

How is the Bragg angle used in real-world applications?

Bragg Diffraction is used in various real-world applications, such as X-ray crystallography for determining protein structures, analyzing crystal structures of minerals in geology, and non-destructive testing in materials science. It is also used in X-ray diffraction techniques for identifying substances in chemistry and in medical imaging for detecting bone fractures and analyzing the composition of materials in the body.

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