Probing The Heart of Matter

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Probing The Heart of Matter
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Yo you guys, its sciences very own Alan Guth!
Hi Im Alan Guth. You may remember me from
such physics lectures as The Inflationary
Universe, When Gravity Goes Wrong, Quarkinator
III and The Joy of Emphasising Your Spectacular
Realization With A Double Box. Im here to tell
YOU about probing. The heart. Of matter.
Arnold, ask the question weve all been waiting
for if you will
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Whatchoo talkin bout, PRO?
Momentum
Kinetic energy, work
Wave
-particle
duality
Force fields
Vectors
Graphs
Circular motion
Inverse-square law fields
Now thats what Im talkin bout!
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Size matters

• Sometimes in the exam youll have to remember the
  approximate size of an atom
• Its easy atoms are about 1 nm in diameter,
  thats 1 x 10-9 m wide
• That also means that the nuclei in atoms that are
  bonded together all around us are about 1 nm
  apart
• Its useful to know this separation distance
  because its the gap size that a diffracting wave
  or particle has to pass through e.g. in x-ray
  diffraction

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Mesons Jekyll and Hyde

• Mesons are made up of two quarks
• They always consist of a quark and its
  corresponding antiparticle
• Mesons are a bit like Dr Jekyll and Mr Hyde two
  alter egos in one place

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Baryons threesomes
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Spot the difference
electromagnetic wave
photon
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Trick question!

• Theres no difference! (Sort of)
• Wave-particle duality means that matter is
  neither a wave nor a particle - its both!
• A very strange idea but nonetheless, it was
  proved by loads of experiments

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The de Broglie Wavelength

• In 1924, French prince and scientist Louis de
  Broglie got a PhD for realising wave-particle
  duality
• His work shows that particles must have a
  wavelength because they can diffract like waves
• Even you have one that means you can diffract

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Rutherford and a-scattering
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Electron diffraction
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Circular motion
v ?r

• Linear velocity angular velocity x radius
• Youre going all the way round a roundabout once
  every 10 seconds
• If the roundabout is 20 m wide, how fast are you
  going?
• If the roundabout is 40 m wide, how fast are you
  going?

? 2p rad 10 s 0.2p rad s-1 r ½m 20/2
10 m So v ?r 0.2p rad s-1 x 10 m 6.3 ms-1
14 mph
? 2p rad 10 s 0.2p rad s-1 r ½m 40/2
20 m So v ?r 0.2p rad s-1 x 20 m 12.6 ms-1
28 mph
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Centripetal acceleration

• Page 67 in AQA A2 Physics
• Recall and use F mv2/r
• F mr?2

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Collisions

• When two particles hit each other, energy is
  conserved, as is momentum and charge
• When a particle and an antiparticle (like an
  electron and a positron) collide, they annihilate
  their energy becomes two gamma rays which fly off
  in opposite directions (so their momentum adds up
  to zero)