A Quantum Journey Quantum Physics And Quantum Physicists

Classical Physics All of physics excluding relativity and quantum mechanics Two distinct ideas in classical physics: PARTICLESWAVES Definite position Definite momentum Point-source of mass Propagation of energy No mass Mechanical or EM displacements

Wavelength Intensity Classical Physics Walks The Planck A black body radiator produces a spectrum characteristic of its temperature Classical Raleigh-Jeans law didn’t work Predicted an ultraviolet catastrophe Classical Physics had failed

Classical Physics Walks The Planck Max Planck spotted the problem Energy is not continuous There is a natural limit to the short wavelength radiation E = hf Energy and waves come in quanta;Waves must be made of particles energy frequency Planck constant = 6.63  Js

Energy, Mass And A Famous German PositronElectron Two photons produced annihilate Mass (particles) converted to Energy (waves) Reverse process: Energy can be converted to mass Energy and mass can be interchanged

Energy, Mass And A Famous German Albert Einstein quantified this relationship E = mc 2 energy speed of light in a vacuum = 3  10 8 ms -1 mass Mass and energy are just different forms of the same thing ANY gain in energy is a gain in mass (and vice-versa)

Wave–Particle Duality Louis-Victor de Broglie combined Einstein and Planck’s equations E = mc 2 E = hf

Wave–Particle Duality 1 wavelength momentum  Property associated with particles Property associated with waves All quantum entities have both particle and wave-like properties A wave when propagating through matter / space Particles when interacting with matter LIGHT

Uncertainty You cannot measure both momentum and position at the same time This is called Heisenberg’s Uncertainty Principle This is NOT due to any limitations of measuring apparatus An electron doesn’t have a precise position and momentum at the same time “We cannot know, as a matter of principle, the present in all it’s details.”

Intensity Distance On Screen The Experiment With Two Holes

Intensity Distance On Screen

The Experiment With Two Holes An electron behaves like a wave, producing an interference pattern Slowing down to one electron at a time produces the same pattern Electrons must have an awareness of past and future If we ‘look’ at each electron, we can see which hole it went through, but we must disturb the electrons to do this The pattern for particles is produced Electrons must go through both holes at the same time But electrons appear as particles (dots) on the screen

The Copenhagen Interpretation It is meaningless to ask what quantum entities are doing when we are not looking at them – they exist as a superposition of states In taking any measurement we must disturb what we are measuring

The Copenhagen Interpretation It is meaningless to ask what quantum entities are doing when we are not looking at them – they exist as a superposition of states In taking any measurement we must disturb what we are measuring

Schrödinger’s Cat The cat will be both dead and alive until somebody looks The Copenhagen interpretation is absurd

The Transactional Interpretation Every charged particle in the universe knows what is happening to every other charged particle Retarded wave Advanced wave Handshake The particle must decide which handshake wave to accept This is given by the laws of probability Gives the same predictions as the Copenhagen interpretation – but gives a different perspective

Conclusion Planck showed that energy occurs in quanta Einstein showed that energy and mass can be interchangedde Broglie demonstrated wave particle dualityHeisenberg incorporated uncertainty into quantum physicsFeynman used the dual-slit experiment to describe quantum physicsBohr promoted the Copenhagen interpretationSchrödinger showed that the Copenhagen interpretation was absurdCramer developed the Transactional interpretation