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Quantum Theory

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Quantum Theory With entangled ... h/(mass x velocity) ... Dirac s improvements of Schrodinger s wave equations Quantum Mechanics gives probabilities Slide 21 ... – PowerPoint PPT presentation

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Title: Quantum Theory


1
Quantum Theory

2
Black Body Radiation
  • Temperature determines the wavelength of emitted
    light.
  • Red hot mostly red light - 3,000 oC.
  • White hot all colors 6,000 oC.
  • http//www.egglescliffe.org.uk/physics/astronomy/b
    lackbody/bbody.html

3
  • It was assumed light could have any energy.
  • The math of the theory did not match the
    distribution of wavelengths observed

4
Max Planck solved the black body radiation
dilemma
  • He created an equation that fit the observed
    distribution of radiation.
  • To do so, he had to assume that energy came in
    packets, called quantum.

5
Plancks Constant
  • Frequency/energy Plancks constant
  • Plancks constant (h) is one of the most
    important constants in nature.
  • (h) 6.626 x 10-34 joule seconds

6
Photoelectric Effect
  • Certain light beams can knock electrons off of
    some metals.
  • This was independent of the intensity of the
    light beam. (total energy)
  • It WAS dependent on the wavelength of the light.

7
  • Short wavelengths have larger quanta (packets of
    energy) to knock off electrons.

8
(No Transcript)
9
Light particle or wave?
  • Light followed the wave equation defined by James
    Clark Maxwell.
  • Light also seemed to exist as packets, like
    particles.
  • The particle/wave designation seems invalid for
    the subatomic world.

10
Particles are also Waves
  • 1923 Louise de Broglie found that matter had
    both particle and wavelike properties.
  • If E hc/wavelength (from Planck) and E mc2
    (from Einstein), than wavelength h/(mass x
    velocity).

11
  • Very small particles exhibit the same wave
    addition and cancellation characteristics as
    waves do.

12
Niels Bohr Planetary Atom
  • Electrons orbit the nucleus in specific circular
    orbits.
  • Problem a charged particle in acceleration emits
    light.
  • Changing direction is a type of acceleration, yet
    orbiting electrons emitted no light.

13
  • http//www.youtube.com/watch?v45KGS1Ro-scNR1

14
Schrodingers Solution
  • The orbit of an electron can only be a whole
    number multiple of the electrons wavelength.
  • The orbital is a standing wave of an electron.
  • There is no changing direction of the electron.

15
  • The electron simply exists in these locations,
    without actually moving from one point to
    another.

16
  • http//www.youtube.com/watch?vFw6dI7cguCgfeature
    related

17
Schrodinger wave equations
  • Any system can be treated as a wave equation in
    quantum mechanics.
  • The orbitals of chemistry are solutions to
    Schrodinger wave equations.

18
  • Electrons materialize from one location to
    another without passing a plane of zero
    probability existence.
  • This is just quantum weirdness.

19
Paul Diracs improvements of Schrodingers wave
equations
  • He generalized the equations to relativistic
    theory.
  • He mathematically explained electron spin with
    angular momentum.
  • He postulated the existence of antimatter based
    on the negative square root of Emc2.

20
Quantum Mechanics gives probabilities
  • 1926, Max Born the square of the wave equation
    gave the probability of finding the particle in a
    given location.
  • Many (Einstein) felt that probability was not
    good enough.

21
  • If we really understood something, we should know
    what will happen and what is really going on
    behind the scenes.

22
  • http//www.twine.com/item/11wp44xsg-xx/youtube-qua
    ntum-mechanics-for-dummies-electrons-are-weird

23
Heisenberg Uncertainty Principle
  • We cannot know both the velocity and location of
    an electron. The more we know about one, the
    less we know about the other.
  • High energy light gives a better location, but
    disrupts the velocity.

24
  • Low energy light disturbs the velocity less, but
    gives high uncertainty of location. Lower energy
    light gives worse resolution.
  • The uncertainty of position times the uncertainty
    of momentum is greater or equal to Plancks
    constant divided by 4p.

25
  • http//www.youtube.com/watch?vKT7xJ0tjB4A

26
Uncertainty vs. Determinism
  • Uncertainty was not just a result of the
    crudeness of the instruments, it was a
    fundamental law of nature.
  • Determinism the idea that you can state the
    future if you know everything about the present.
  • Einstein favored determinism, but uncertainty was
    found to rule.

27
Double slit experiment
  • The same results are obtained with light,
    electrons, or any other type of wave.
  • http//www.youtube.com/watch?vDfPeprQ7oGc
  • How does the particle going through the slit
    know that the other slit exists?

28
  • Since the electron, like all matter, has wave
    characteristics, its final location is defined by
    the probability given by the square of the wave
    equation for the given system it is in.

29
Bells Theorem
  • John Bell used a thought experiment and logic to
    prove that reality is non-local.
  • Non-local means objects are affected by distant
    objects and events that cannot reach them with a
    force, because they are outside of the light cone.

30
  • Outside the light cone, signals or forces from
    one object must travel faster than the speed of
    light to create the observed behavior.

31
Quantum Entanglement
  • When two particles or events affect each other
    without any signal or force.
  • Determinism, and our common sense, says that this
    is totally impossible.
  • http//calitreview.com/51

32
  • Quantum mechanics predicts when it will or will
    not happen, and what the probability of the
    outcome will be.
  • http//www.youtube.com/watch?vJh8uZUzuRhkfeature
    related

33
Collapsing Probability Waves
  • Quantum mechanics says that the measurement of a
    particle, such as an electron, collapses the
    probability wave to a single event.

34
  • With entangled particles, the measurement of one
    collapses both of their probability waves
    simultaneously.
  • Any interaction, human or not, collapses
    probability waves.

35
  • http//www.youtube.com/watch?v9lOWZ0Wv218feature
    related

36
Quantum Theory and the Universe
  • Cause and effect gives way to probability.
  • The things you do can instantaneously affect
    things far away (non-local).

37
  • Events can happen without a force or signal to
    cause it to happen - the fabric of space allows,
    or even causes it to happen.
  • Objects do not always have specific properties
    until they are interacted with the properties
    hang in some sort of limbo.

38
The Standard Model
  • This is the current quantum theory.
  • Many new subatomic particles have been
    discovered.
  • There are three families of particles.

39
  • Each family contains two of the quarks, an
    electron (or one of its cousins), and one of the
    neutrinos.
  • These are the building blocks of all matter.

40
Four Force Particles
  • Strong force The gluon holds the nucleus
    together.
  • Weak force The W and Z bosons cause
    radioactivity.
  • Electromagnetism The photon causes light.

41
  • Gravity The graviton is the cause.
  • Experiments have established all force particles
    except the graviton.
  • Gravitons are expected to be discovered soon.

42
Standard Model Equation
  • It uses an input of 19 pieces of information,
    which are properties of the force and mass
    particles.
  • It has been flawless at predicting experimental
    outcomes as probabilities.

43
  • Everything that happens in the universe, besides
    gravity, can be predicted by the Standard Model.
  • Newtons equations fall out of Standard Model for
    normal conditions.

44
Particle Behavior
  • The uncertainty principle allows for extreme
    particle behavior on the subatomic level.

45
  • There is a trade off between the energy a
    particle has and the time it takes to measure
    this energy, which allows the energy of a
    particle to fluctuate wildly over a very short
    duration of time, called the quantum jitters.
  • Tunneling is allowed.
  • http//www.youtube.com/watch?v6LKjJT7gh9sfeature
    related

46
More Unification
  • Steven Weinberg and his colleagues unified the
    weak and the electromagnetic forces.
  • They won a Nobel Prize for this work.

47
Weaknesses of Standard Model
  • It explains how nature behaves, but not why it
    behaves in the way it does.
  • It does not include gravity therefore, it cannot
    be a complete theory of the universe.
  • Its use is primarily for the subatomic level.

48
A few good web-pages
  • http//www3.hi.is/hj/QuantumMechanics/quantum.htm
    l
  • http//www-groups.dcs.st-and.ac.uk/history/HistTo
    pics/The_Quantum_age_begins.html
  • http//www.youtube.com/watch?vyLprHMq4ZkMfeature
    related
  • http//www.youtube.com/watch?vXEZtw1yt8Kcfeature
    related

49
  • http//www.youtube.com/watch?v1_HrQVhgbeofeature
    related
  • LAC collider http//www.youtube.com/watch?v1_Hr
    QVhgbeofeaturerelated
  • Quark song http//www.youtube.com/watch?vU0kXkWXS
    XRAsafety_modetruepersist_safety_mode1

50
????? Wild possibilities or psudoscience?
  • http//www.youtube.com/watch?vfLLIkTo4KLc
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