Braggs' experiment (1 Viewer)

[nomz]

What / how much do we need to know about Braggs' experiment? I was away when we did it in class and I don't really get it. Would any body please give me a brief run down of what we need to know? Much appreciated.

 

[JayWalker]

Braggs Experiment..
I think this hit to my head has damaged my memory ... which experiment is this?!
I think this is the one referred to as "Rutherfords scattering" ?!? Err wait
No Bragg = Diffraction?
Is this the one where he fired X rays at an element, and he picked up a diffraction pattern that was linear that proved that the atoms in a conductor were in an arranged order?!

Uhh pls help

 

[nomz]

yeah it had something to do with X-ray diffraction, but I really don't get it!

 

[sub]

x-rays fired at a nickel lattice structure, and the x-rays bounced off both the top lattice and the second lattice. by working out the difference in the wave interference the distance between the two lattices could be worked out...
this experiment gave the same results for all nickel crystals indicating that it was true for all nickel crystals...therefore they worked out that crystals have regular structure...
i hope that helps

 

[JayWalker]

thats the one!!!

 

[sub]

hangon...i get confused between the davisson and germer one and the braggs experiment...so in case:

the davison germer one is (i think...it could be the other way around)...is the one where they fire electrons at the nickel crystal and then it diffracts (not bouncing off at the right angles)...and thus proving deBroglie's wave/particle duality as diffraction is a wave property...

which one's which? is this the davisson/germer one?

 

[JayWalker]

hangon...i get confused between the davisson and germer one and the braggs experiment...so in case:

the davison germer one is (i think...it could be the other way around)...is the one where they fire electrons at the nickel crystal and then it diffracts (not bouncing off at the right angles)...and thus proving deBroglie's wave/particle duality as diffraction is a wave property...

which one's which? is this the davisson/germer one?

You got it right..

The Davison Germer one using nickel crystal, andi t had a specific diffraction pattenr, an attribute only assigned with waves, hence the wave partciel nature..

 

[sub]

excellent...im not as screwed as i first thought

thnx for clearing that up

 

[gordo]

so wats the difference between braggs exp and davison/germer exp?

 

[Jase]

Nickel? Isn't that the Davisson Germer one, where they shot electrons at annealed nickel alloy to observe diffraction.

Bragg's one is the one where they shoot X-rays at a crystal using Von Laue's reflecty method. It's like.. imagine a crystal has layers, and each layer has a couple of atoms evenly spaced across. You shine some X-rays at it, one beam hits the top layer and bounces off. Another beam passes through the first layer and hits the second and bounces off. The two bouncing off beams interfere with each other because the second one obviously had to travel a little bit more than the first one. So they're unevenly reflected. then there's a pattern of rings on the photoplate. They measure the path difference or the gap between each ring to find a value of dsin@..

and using some simple trig and geo, you get the exact spacing between those two layers.
using the forumla nw = dsin@ where w is wavelength of Xray and @ is the angle of incidence.

 

[JayWalker]

Nickel? Isn't that the Davisson Germer one, where they shot electrons at annealed nickel alloy to observe diffraction.

Bragg's one is the one where they shoot X-rays at a crystal using Von Laue's reflecty method. It's like.. imagine a crystal has layers, and each layer has a couple of atoms evenly spaced across. You shine some X-rays at it, one beam hits the top layer and bounces off. Another beam passes through the first layer and hits the second and bounces off. The two bouncing off beams interfere with each other because the second one obviously had to travel a little bit more than the first one. So they're unevenly reflected. then there's a pattern of rings on the photoplate. They measure the path difference or the gap between each ring to find a value of dsin@..

and using some simple trig and geo, you get the exact spacing between those two layers.
using the forumla nw = dsin@ where w is wavelength of Xray and @ is the angle of incidence.

Yeah thats right, you had to assume a crystal is like an ogre, it has layers...

 

[nomz]

thanks guys! big help. We didn't do the davison one? Do we have to know it?
All the best for the exam on wednesday everyone!

 

[sub]

Nickel? Isn't that the Davisson Germer one, where they shot electrons at annealed nickel alloy to observe diffraction.

Bragg's one is the one where they shoot X-rays at a crystal using Von Laue's reflecty method. It's like.. imagine a crystal has layers, and each layer has a couple of atoms evenly spaced across. You shine some X-rays at it, one beam hits the top layer and bounces off. Another beam passes through the first layer and hits the second and bounces off. The two bouncing off beams interfere with each other because the second one obviously had to travel a little bit more than the first one. So they're unevenly reflected. then there's a pattern of rings on the photoplate. They measure the path difference or the gap between each ring to find a value of dsin@..

and using some simple trig and geo, you get the exact spacing between those two layers.
using the forumla nw = dsin@ where w is wavelength of Xray and @ is the angle of incidence.

hey maybe ur right, cos it sounds right...but we were taught that the crystal u mention was a nickel crystal, so basically its the same shit...

yeah, and best of luck on wednesday

 

[Jase]

Davisson and Germer is quanta to quarks, im guessing you don't do that.. so you won't have to worry about it!

Oh and just clearying up the stuff about nickel ... it's all the same!
As long as it's a crystal..

Like, historically, Davisson used Nickel.
And Braggs i think used Sodium Chloride or something.

But it would work with any kind of crystal with a nice spacing between.

 

[superbird]

just know the diagram and the basics of the experiement. basically braggs prooved the lattice structure within atoms when they fired electrons into a crystral. main principle: xray diffraction

 

[nomz]

nah I do medical physics. Cool that clears it up, thanks... I was stressing for a while there!

 

[DavidB]

just know the diagram and the basics of the experiement. basically braggs prooved the lattice structure within atoms when they fired electrons into a crystral. main principle: xray diffraction

HUH??? Fired at electrons into a crystal? wait a secont...

Braggs experiment:
he subjected a metallic lattice to X-rays (small wavelength meant that the waves would reflect off the atoms)...and the reflecting waves would undergo superposition interacting destructively and constructivly so that when they were allowed to shine onto a projecting material, they would form dots of high concentration.
He took parametres and subbed them into an eqn to find d.

true/false?

peace.

 

[sub]

true...x-ray diffraction is the same thing as firing electrons...(i think)

 

[Jase]

Those two arent quite the same, It's the same pattern and same principle.
But Davisson and Germer used a different method to discover completely different things (discluding the fact that they used electrons). All they did was shoot electrons into one crystal and it reflected/scattered off the surface randomly and created a diffraction pattern.

Anyway, why am i still talking about this? case closed haha.

 

[senso]

davisson and germer proved the wave-particle duality of electrons by shooting them at a nickel crystal and notiving the constructive and destructive interference, which resulting in maxima and minima.

The Braggs shot x-rays at a crystal specimen and knowing the wavelengths and such analysed the resulting maxima and minima diffracted from the crystal to learn about the crystal structure of metals