# What is Bragg: Definition and 83 Discussions

Sir William Henry Bragg (2 July 1862 – 12 March 1942) was an English physicist, chemist, mathematician, and active sportsman who uniquely shared a Nobel Prize with his son Lawrence Bragg – the 1915 Nobel Prize in Physics: "for their services in the analysis of crystal structure by means of X-rays". The mineral Braggite is named after him and his son. He was knighted in 1920.

View More On Wikipedia.org
1. ### I Can Geant4 Simulate Alpha Particles in a Bragg Chamber?

Me and my colleagues need to analyse data from a Bragg chamber. We have sources of Cm244, Am241, Np237 sending alpha particles in the chamber which is fill with Argon and CH4 at 1%. Is there any software that can simulate di situation ? I downloaded SRIM but i’m not sure it is the best one for...
2. ### I Bragg condition and Bloch states

I'm reading about Bloch states, these the are states of electrons in a periodic potential. What i know is that the electron in a Bloch state is shared between many ions and it is a stationary state. However, for a 1-dimensional model I've read that at the edge of the first Brillouin zone, when...
3. ### Bragg angle with an inclined plane through a square lattice

Suppose a square lattice. The planes are such as the image below: I light wave incides perpendicular to the square lattice. The first maximum occurs for bragg angle (angle with the plane (griding angle) as ##\theta_B = 30°## (blue/green), green/blue in the figure). The angle that the...
4. ### Bragg curve -> observing dependence on velocity

We can read: "The velocity dependence of the stopping power, increasing with decreasing velocity, is obvious from Fig.4". I know why the stopping power depends on velocity as Bethe equation states, but I do not know how I can observe that dependence on a Bragg curve.
5. ### The possible plane separation related to Bragg reflection

2d sin q = nl d = nl / (2 sin q) d = (1 x 0.16) / (2 sin 30o) = 0.16 nm But 0.16 is not in the option. And how to find other value of d? Thanks
6. ### I What explains the sharpness of XRD peaks?

I was reviewing an old topic for me that's x-ray diffraction, and one doubt I always had in my mind arised again. When introducing the Bragg's law, the typical explanation is that the x-ray waves reflecting in two adjacent planes interfere with each other, leading to a fully constructive...
7. ### A Plotting a Bragg Curve in SRIM

I'd like to plot a Bragg curve for an alpha particle in air. I'd like to make one plot for 239Pu (5.156 MeV alpha) and one plot for 238U (4.267 MeV). Does anyone know how I can do this? I would like a basic plot of stopping power (MeV/cm) vs path length (cm). Thank you
8. ### I Where do I get raw data for plotting Bragg curve?

Hi people, I am looking for a database where I can get raw data to plot the Bragg's curve for alpha particles energy loss vs range in Silicon, Germanium and CZT. Your help will be much appreciated. Cheers, Shri
9. ### Bragg diffraction form an “inclined” crystal plane

Homework Statement In picture, first-order reflection from the reflection planes shown occurs when an x-ray beam of wavelength ##0.260 nm## makes an angle ##\theta=63.8°## with the top face of the crystal. What is the unit cell size ##a_0##? Homework Equations Bragg law d=\frac{ n...
10. ### A Energy gap between energy bands in solid state physics

I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands. In this picture below you can see the probability density of a symmetric (+) and anti-symmetric (-) standing wave. The...
11. ### I Identification of index of Bragg peaks for NaCl

In my x-ray crystallography data for a single crystal of NaCl using x-rays generated by Cu k alpha (154 pm), there are three peaks identified at angles of 14.155, 31.475 and 53.5 degrees. According to http://www.nada.kth.se/~fabo02/solid/xray.pdf, these peaks must correspond to only even values...
12. ### I How to index single crystal Bragg peaks

I am able to find methods on how to index Bragg peaks for powder diffraction, and was wondering if the method is the same for single cubic crystals of NaCl? I have tried and cannot get the expected sequence of allowed reflections for cubic lattices (h^2 + k^2 + l^2= 3, 4, 8, 11, 12, 16, 19...
13. ### I Davison-Germer experiment - Bragg condition

Hey, I'm trying to adapt the Bragg condition for the David-Germer experiment, so I can then use their experimental results to show that the measured wavelength is compatible to the wavelength theorized by De Broglie. However I'm having issue with the calculation, any help would be much...
14. ### Bragg Law & Diffraction Condition

Hello. I am reading "Introduction to Solid State Physics" by Kittel and there is a derivation in the textbook that I am understanding. This should be a fairly simple question but I am unable to see it. 1. Homework Statement In Chapter 2, it derives the Bragg law using the diffraction condition...
15. ### Deducing Bragg angle for G_220 Bragg peak for LiF

Homework Statement Calculate the reciprocal lattice vectors for LiF. Given the lattice parameter ##a = 0.402 nm## calculate the magnitude of the ##\textbf{G_{220}}## reciprocal lattice vector for LiF and thus deduce the Bragg angle for the (2,2,0) Bragg peak for incoming wavelength of ##0.9...
16. ### Bragg Diffraction: Calculate 1st & 2nd Order Angles

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...
17. ### Linearly Chirped Fiber Bragg Grating group delay

Homework Statement Here is my problem : I want to know where does group delay equation come form? Homework Equations As I checked reference 21 it only indicates The Attempt at a Solution I'm following how can I start and solve this problem
18. ### MATLAB Center Wavelength of Fiber Bragg Grating Filter

I would like to locate the center wavelength of a FBG notch filter in MATLAB, but I'm having trouble getting an answer within 0.01nm of the correct wavelength. So far I've tried using a quadratic fit with MATLAB, but that is too dependent on the amount of data points to the left and right of...
19. ### Misconceptions about Bragg scattering and how it works

Homework Statement Briefly describe how diffraction through a crystal lattice could be used to isolate a single wavelength from X-rays of many wavelengths. Homework Equations Bragg's equation: 2dsin(Θ)=n*λ The Attempt at a Solution Pretty fundamental question for the lab that I am about to...
20. ### X-Ray Diffraction in Crystals: Exploring Scattering & Interference

In explaining x-ray diffraction of crystals, usually the approach is to consider the atoms absorb radiation and scatter it, at some angles constructive interference occur and bright spots can be observed. It seems that it is different from the diffraction of slits or gratings because in these...
21. ### Why is there reflection in 222 plane of Silicon?

We know that silicon has a FCC lattice with basis at [0,0,0] and [1/4,1/4,1/4]. The structure factor is S_{(hkl)} = \left[1 + e^{i\pi(h+k)} + e^{i\pi(l+k)} + e^{i\pi(h+l)} \right] \left[ 1+e^{i\frac{\pi}{2}(h+k+l)} \right] which should be zero for (222) plane. But measuring it carefully...
22. ### Is Bragg Diffraction Depicted Accurately in Common Diagrams?

Hi. So I am studying a bit on acousto-optics and as far as I've gathered, when the Bragg condition is met, the incident ray of light should just be reflected (in a perfect case) with the angle of reflection equal to the angle of incidence. However, this picture does not agree with my thoughts...
23. ### Diffraction orders of grazing incidence

Homework Statement We have a honeycomb lattice. There is an incident wave of 400 nm, whose wavevector has an angle of 75 degree with the surface's normal. This problem is similar to LEEDS ( low energy electron diffraction). Homework Equations What is the condition of diffraction i.e. which...
24. ### Does the Bragg equation hold for arbitrary diffractions?

Any proof I look up of the Bragg law proves a simplified case of the situation. The most common one is where both rays reflect on points that are perfectly on a vertical line like this: http://pms.iitk.ernet.in/wiki/images/thumb/Jk2_1.png/400px-Jk2_1.png The second most popular case is to...
25. ### Fiber Bragg Gratings Reflection Co-efficient

I am studying fiber bragg gratings for a project. I read the couple-mode theory and came across a plot of the reflection coefficient v/s wavelength used which had a global maxima at the Bragg wavelength. The plot was drawn for a constant value of the coupling constant κ. I don't understand this...
26. ### Minimum Energy for Bragg Reflection in Cubic Crystals

Homework Statement A cubic crystal has a spacing between atoms of d = 0.2 nm. What is the minimum energy for X-rays such that non-trivial Bragg reflection may occur (peak with n =1)? Write your answer in units of keV. Homework Equations 2dsinθ = nλ The Attempt at a Solution i have no idea...
27. ### Bragg law vs interference equaiton

The condition for constructive interference is: n*lambda=d*sin(alpha) Bragg's law is n*lambda=2d*sin(alpha) The diffraction from a crystal cell will also create an interference pattern, so why do these equations differ?
28. ### FBG Wavelength Reflection in Double-Clad MMF for 910 nm Laser Diode

Hi everyone! I use a FBG in a double-clad multimode optical fiber of 20 µm core diameter, and a laser diode working at 910 nm as ligth source. As the Bragg reflection wavelength of a FBG depends on the effective refractive index of the different guided modes (λFBG=2.neff.Λ , where Λ is the...
29. ### Bragg Diffraction Homework: Find Longest Wavelength for 2 Interference Maxima

Homework Statement A beam of 3.55keV X-rays is directed at a crystal. As the angle of incidence is increased from zero, a first strong interferece maximum is found when the beam makes an angle of 18.0o with the planes of the crystal. Calculated d=5.67x10-10 from this (distance between...
30. ### Solve Bragg Diffraction: n(λ)/2sinθ

Bragg diffraction of microwaves lab. Hey guys I have a quick question so for bragg diffraction the formula is 2dsin(theta) = n(lambda). So I have to solve for d, which is d = n(lambda)/(2sin(theta)), but here is the problem: I'm not entirely sure what theta is, as I'm using a graph with 2 peak...
31. ### How does x-ray diffraction from different Bragg planes add up?

I'm writing a little bit of Mathematica code that should be able to make a reasonable powder diffraction spectrum. The algorithm is like this: Take Bravais lattice and basis. Compute reciprocal vectors. Compute structure factor (and its square magnitude) Have triple nested loop that creates...
32. ### How to Design FP resonator from Bragg mirror in Matlab?

Homework Statement Below is a {MATLAB}code for Bragg mirror. How can I implement the code to create an FP resonator? Homework Equations The Attempt at a Solution %User input parameters num_layers = input('The Number of Layers in the structure = '); r_index1 = input('refractive...
33. ### Question about Bragg diffraction

For diffraction to occur in crystal, Bragg equation must be satisfied and h,k,l must be of certain combination. I would like to ask 1. How to distinguish a second order diffraction of (100) and first order diffraction of (200)? (they occurs at the same angle.) 2. How can a (200) plane...
34. ### Exploring Bragg Peak Intensity Ratios in Ca and CaF2 X-Ray Diffraction Patterns

Question statement: We are given that Ca and CaF2 are both Ca face-centred cubic lattices, and that in the case of CaF2 there is a basis of F ions at +/-(1/4, 1/4, 1/4). Then explain qualitatively how the ratio of the (2 0 0) and (4 0 0) Bragg peak intensities in the X-ray diffraction patterns...
35. ### Bragg and Brillouin diffraction

I'm supposed to give a seminar tomorrow for my 300 level experimental physics paper. The experiments we do our reports on are pre-determined and I pulled the short straw with the most bloody complicated on here, the acousto-optic modulator. I'm trying to get my head around it and I've spend the...
36. ### Bragg Angles and Thermal Expansion

Problem statement: The Bragg angles of a certain reﬂection from copper is 47.75◦ at 20◦C but is 46.60◦ at 1000◦C. What is the coeﬃcient of linear expansion of copper? (Note: the Bragg angle θ is half of the measured diﬀraction (deﬂection) angle 2θ). Attempt at solution: Using...
37. ### How Do You Calculate the Cube Edge of Iron Using Bragg's Law?

Homework Statement The bragg angle for reflection from the (110) planes in bcc iron is 22 degree's for an x-ray of wavelength = 1.54 angstroms. Compute the cube edge for iron. Homework Equations 2dsinθ=nλ ? The Attempt at a Solution I feel woefully underprepared for this problem and...
38. ### How Does Copper's X-ray Wavelength Relate to Aluminum's Bragg Angle Calculation?

Homework Statement I'm a bit confused by this question. It starts off by saying a Cu target emits an x-ray line of wavelength λ=1.54 Angstroms. It then goes and says part A of the problem.. A) Given that the Bragg angle for reflection from the (111) planes in Al is 19.2 degrees, computer the...
39. ### Bragg diffraction - How to make sense of it ?

Bragg diffraction - How to make sense of it ?? Is there a way to make sense of Diffraction of X Rays without taking recourse to oversimplified concepts like "Reflection of X Rays by parallel planes" which is generally the explanation in most basic physics books. It's been a couple years since I...
40. ### Coefficient of linear expansion / Bragg peaks

Homework Statement Measurements of XRay scattering from a metal are made. The bragg peaks are θ = 53° and 48° for temperatures of 300K and 1272K. What is the linear expansion coefficient? Homework Equations linear expansion coef is given by (1/L)(dL/dT) Bragg equation (differential...
41. ### LAB: Bragg Diffraction Grazing Angle Error

Homework Statement I wasn't sure where to post this question. I hope I picked the right section of the forums. This is from intermediate lab. The lab is for Bragg diffraction using microwaves. The grazing angle is a measured quantity along with the voltage (which was measured using an...
42. ### How Does the Cell Constant d Relate to Diffraction Angles in Bragg's Law?

How is the cell constant "d" related to the cell parameters? I know that for the smallest possible diffraction angle d is equal to the longest cell edge. Why?
43. ### Missing Reflections in FCC/BCC Crystals: Bragg Model Inadequate?

I noticed that using the Laue equations reflections from some of the planes in the fcc and bcc crystal are not allowed. Now using the (maybe too naive?) Bragg model we can always find Bragg peaks whichever plane we hit with waves. So is the Bragg model too simple for these planes? And what is it...
44. ### Why Must the Wavelength Be Smaller Than the Interplanar Spacing in Bragg's Law?

Hello everyone I would like to ask you something related to the investigation of materials depending on Bragg Diffraction (Bragg Law). It is a prerequisite, that the wavelength of the used radiation must be smaller than the dimension of the sample, by the meaning λ ≤ d , where λ is the...

46. ### Bragg Law and Effect of Doubling Wavelength

My lecturer discussed bragg's law a few weeks ago and described how the angle theta changes as the wavelength is doubled. I can't seem to duplicate his result. I know that the bragg condition for a maxima would reduce to : dsinθ=mλ when the wavelength is doubled. In his example he knew...
47. ### Why Does Bragg Diffraction Occur for Bound Electrons in a Crystal?

As far as I know, Bragg diffraction happens for incident particles which are free; for example free electrons or X-ray are Bragg-reflected under the special conditions. Why the Bragg diffraction happens for electrons which are not free in a crystal?
48. ### Calculation of InAS WurtZite bragg peak position

Hey If I have a InAs Wurtzite structure, and now the a and c parameter from tables. How can i calculate the distance between (1 0 3/2)_sur layers? (in surface coordinates) I need it to find the angle of reflection, for a (1 0 3/2) WZ InAs peak. Is it just so simple? (1 0 3/2)_sur =...
49. ### Calculation of the first two X-ray Bragg reflections from KCl and KBr

Homework Statement HI, I am practicing some exam questions to get ready for a repeat, below is the question I am having trouble with. "The lattice constants of KCl and KBr are 6.29 angstroms, and 6.59 angstroms, respectively. What would be the first two observed Bragg diffraction angles...
50. ### Fiber bragg grating and pressure

hello,i just want to know how the fiber bragg grating is being affected by the pressure that act on it? and where is the reference that i can refer to further reading..thanks