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Lesson 10: Quantum Physics Lecture Outline
What is Quantum Physics? • Quantum physics: Describes the interaction between atoms and light (ie, particles & waves that are nanometers in size, or less) • An amount is quantized if it can only have a specific set of allowed values
The Quantization of Light • Light is emitted or absorbed in quantized amounts (ie, particle-like behaviour) ─ Proof: photoelectric effect • All waves are quantized in energy, but this is undetectable in waves with λ > atoms (so classical physics applies) • Photon (γ): a particle of light ─ ie, red photons are “bigger” (and lower in energy) than blue photons, and a highamplitude wave has “many” photons
Quantum Leaps and Spectroscopy • Bound electrons absorb and emit energy in quantized amounts, depending on the electron’s orbit in its atom ─ allowable orbits are energy states; forbidden orbits are energy gaps • Quantum leap: When an e- switches orbits, it emits (or absorbs) a γ with energy equal to the difference between the orbits • Spectroscopy: the determination of a light source’s chemical composition from absorption & emission lines in its spectrum
Lasers • Laser: a light source produced by Light Amplification by Stimulated Emission of Radiation ─ Laser light is monochromatic, coherent and highly directional • CD/DVDs: data is read by reflecting a laser off micron-sized bumps on the disk ─ DVDs: smaller bumps on multiple layers for greater storage • Laser surgery: focuses laser light on a precise spot; intense heat can cut, cauterize, weld or carve/reshape
Electronics and Semiconductors • Semiconductor: a substance in which the allowable energy states of bound electrons are arranged in bands & gaps (eg, silicon crystal) • This enables precise control over electron flow, making electronics possible ─ Eg, solar panels, battery chargers, LEDs, digital camera, computer processors, and countless others
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