Presentation on theme: "Wave-Particle Duality: The Beginnings of Quantum Mechanics"— Presentation transcript:
1 Wave-Particle Duality: The Beginnings of Quantum Mechanics
2 Explain the basics of wave-particle duality. Define the relationship between quantum, photon and electron.Describe how a produced line spectra relates to the Bohr diagram for a specific element.Additional KEY TermsAbsorption Spectra Threshold energy
3 PHOTOELECTRIC EFFECTUnder certain conditions, shining light on a metal surface will eject electrons.Electrons given enough energy (threshold energy) can escape the attraction of the nucleus.*Light is acting like a “particle” in this experiment – collision.
4 Can only explain it if you think of it using photons in a collision. Only high frequency light (> 1.14 x Hz) will eject electrons - acting as particle.Can only explain it if you think of it using photons in a collision.
5 Only more intense light (higher amplitude) will eject more electrons - acting as wave. Can only explain it if you think of it as changing the size of the wave.
6 Photons have no mass but carry a quantum of energy. Einstein (1905) - electromagnetic radiation is a stream of tiny bundles of energy called photons.Photons have no mass but carry a quantum of energy.One photon can remove one electron.Light is an electromagnetic wave, yet it contains particle-like photons of energy.
7 Compton (1922) – first experiment to show particle and wave properties of EMR simultaneously. Incoming x-rays lost energy and scattered in a way that can be explained with physics of collisions.
10 Bohr (1922) – restricting electrons to fixed orbits (n) with different quantized energy levels. Created a math equation for energy of each orbit.Equations correctly predicted theline colours of hydrogen spectra.Energyn = -(2.18 x J)/n2
11 Electron absorbs radiation and jumps from ground state (its resting state) to a higher unstable energy level (excited state).Electron soon loses energy and drops back down to a lower energy level – emitting the absorbed EMR.AbsorptionIonizationFree Atome−EMREMRe−Excited Statee−Ground Statenucleus> Threshold Energy< Threshold Energy
12 ΔE = E higher-energy orbit - E lower-energy orbit = Ephoton emitted= hf
13 Levels are discrete like quanta – no in between. Each jump/drop is associated with a specific frequency photon - same transition, same photon.
14 The size of nucleus will affect electron position around the atom – and the size of “jump” energy.
15 *Each element has a unique line spectrum as each element has a unique atomic configuration.
16 Emission spectrum – portion of visible light emitted by that element – cooling down. Absorption spectrum – portion of visible light absorbed by an element – heating up.
17 CAN YOU / HAVE YOU?Explain the basics of wave-particle duality.Define the relationship between quantum, photon and electron.Describe how a produced line spectra relates to the Bohr diagram for a specific element.Additional KEY TermsAbsorption Spectra Threshold energy