Looking Inside The Atom Flashcards

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1
Q

Rutherford scattering experiment?

A
  • alpha particle fired amd thin gold foil
  • most went straight through so atom is mostly empty space
  • some were deflected through large angles so centre must be positive to repel them
  • very few scattered more than 90 degrees so nucleus must be tiny but more massive than the alpha particle
  • most of mass must be in nucleus as fast particle still deflected
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2
Q

How to calculate distance of closest approach?

A

-refelcts when epe is equal to ke so
Initial K.E=electrical potential energy=kq(alpha)Q(gold)/r
-r is distance of closest approach ie distance from nucleus

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3
Q

How to find charge of nucleus

A

-proton has same charge as e
-So no of protons x charge of e
-

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4
Q

What is the charge of an alpha particle?

A

+2e

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5
Q

What is a hadron?

A
  • Particles that have strong interactions
  • reason protons and neutrons are held when they repel
  • made up of quarks
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6
Q

What are two hadrons and how do they differ?

A
  • Proton a stable hadron
  • neutron is a unstable hadrom that decays into a proton caused by the weak interaction when not in the nucleus
  • reaction is n ~> proton + electrom +antineutrino
  • neutrons not in the nucleus have a half life of 15 mins
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7
Q

Whats a lepton

A

-Particle that interact via the weak interactions and gravity

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8
Q

What 2 leptons od we need to know?

A
  • electrons (-1 charge)

- neutrinos (0 charge 0 mass) symbol of v (but curvy), neutrinos only experience the weak interaction

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9
Q

What is lepton number?

A

-number of leptons, electrosn and neutrinos is 1

Always conserved

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10
Q

What is an antiparticle?

A

A corresponding particle w same mass but opposite charge

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11
Q

What happens when energy is converted to mass

A
  • equal amounts of matter and anti matter
  • this is called pair production
  • draw diagrams and check them in book
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12
Q

When does pair production happen?

A
  • when one photon has enough energy to produce that mass
  • near a nucleus to ocnserve moentum
  • usually get low mass particle
  • calculate minimum energy using Erest=mc^2
  • draw squiggly line into two curved lines of opposite particle
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13
Q

What is annihilation?

A
  • particle and antiparticle meet
  • total mass converted to energy forming pair of identical photons
  • use Ephoton=mc^2 to calculate the min energy of photons
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14
Q

What are we assuming as negligible in annihilation?

A

Kinetic energy

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15
Q

How long do amtiparticles exist for?

A

Fraction of a secomd so quickly anihilate after pai creation

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16
Q

What are fundamental particles?

A

Quarks

17
Q

What quarks do we need to know?

A
  • Up quark, symbol u, charge +2/3
  • down quark,symbol d, charge -1/3
  • also there anti quarks
18
Q

What quarks make a proton?

A

uud

=+2/3 +2/3 -1/3

19
Q

What quarks make a neutron?

A

udd

= +2/3 -1/3 -1/3

20
Q

What happens when u try sepertae quarks with lots of energy?

A

Energy transfeered to mass so pair production

21
Q

Each one of the 4 fundamental forces in nature has its own….

A

Gauge bosons (exchange particles when they interact)

22
Q

What is the gauge boson that causes the strong interaction and how does it cause pair creation?

A

Gluon
Causes strong foce in hadrons (protons and neutrons)
-when quarks in hadrons are pulled apart the energy in gluon field increases until a quark + anti quark pair is produced

23
Q

How does a linear particle accelerator work?

A
  • long straight tube of electrodes
  • connected to alternating pd supply so charge of electrode keeps changes from + to -
  • timed so particles always attracted to the next electrode and reppeled from current ome
  • speed increases each time so can approach speed of light
  • collide w fixed target at end of tube
24
Q

Whats a synchrotrons?

A

-circular accelerator w two beams in opposite directions so can produce very high energy collisions

25
Q

When speed of object is approaching c it…

A

Gets more massive

26
Q

How does the fact that electrons are fermions effect there energy levels?

A

Means no more than 2 electrons cqn be in the same energy level at the same time

27
Q

How do wave models of atoms help us understand energy levels?

A

-when they orbit a nucelus follow pattern of standing wave
-one orbit fits n lambda like standing waves
-think lf electrons like being trapped in a potential well so can be represend by two walls showing energy levels
-electrons can escape when KE+PE>0
Diameter of atom (distance between walls) to ifnd de brogile wavelength