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MODERN PHYSICS

MODERN PHYSICS. Going inside the Atom. Light is a wave. Or is it?. Wave-Particle Duality. Photoelectric Effect (light behaves like a particle) Compton Effect (light behaves like a particle) Entirely new theory needed!. Quantum Theory.

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MODERN PHYSICS

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  1. MODERN PHYSICS Going inside the Atom

  2. Light is a wave. Or is it?

  3. Wave-Particle Duality • Photoelectric Effect (light behaves like a particle) • Compton Effect (light behaves like a particle) • Entirely new theory needed!

  4. Quantum Theory • Electromagnetic energy is emitted from and absorbed by matter in discrete amounts or packets (a quantum). • The amount of energy of a quantum is given by E = hf, where h is Planck’s constant and f is the frequency of the radiation. • The quantum of electromagnetic energy is called a photon.

  5. Models of the Atom • Thomson’s Model (M&M cookie) • Rutherford’s Model • Bohr Model

  6. Assumptions of the Bohr Atom I • All forms of energy are quantized, that is, an electron can gain or lose kinetic energy only in fixed amounts, or quanta. • The electron in the hydrogen atom can occupy only certain specific orbits of fixed radius and no others.

  7. Assumptions of the Bohr Atom II • The electron can jump from one orbit to a higher one by absorbing a quantum of energy in the form of a photon. • Each allowed orbit in the atom corresponds to a specific amount of energy. The orbit nearest the nucleus represents smallest amount of energy that the electron can have. Electrons do not lose energy in these orbits.

  8. Energy Level Diagrams • When an electron falls from a higher energy level to a lower one, the atom emits a photon with energy equal to the difference between the energies of the initial and final states. • Ephoton = Ei - Ef • See Reference tables

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