2 Light Is a WaveAmplitude is the height of the wave from zero to the crest or from zero to the trough
3 Wavelength is the length between waves (how’s that for a definition) Measure crest to crest or trough to troughSymbolized with the Greek letter lambda (λ)Greek Lamb
4 Frequency is the number of waves that pass a given point over a period of time Commonly measured in the unit Hertz (Hz) or sometimes in s-1Symbolized with the letter f
5 The speed of light is 3 x 108 m/s Symbolized with the letter “c” (latin celeritas = swift)We can draw a relationship between wavelength and frequency with the following equation:c = λfQ: What type of relationship does this represent?A: Inverse
6 Try this one!X-rays emitted by Cu have a wavelength of 1.54 x 10-8cm. What is the frequency of this radiation?Answer…1.95 x 1018 sec–1 (Hz)DO WORK!
7 Calculate the wavelength of yellow light emitted by a sodium lamp Calculate the wavelength of yellow light emitted by a sodium lamp. The frequency is 5.0 x 1014 Hz.Answer…6.0 x 10-7m
8 What is the wavelength of radiation with a frequency of 1.50 x 1013 Hz? Answer…2.00 x 10-5m
9 What frequency is radiation with a wavelength of 5.00 x 10-8m? Answer…6.00x1015 Hz
10 The Electromagnetic Spectrum See Page 139 in your book!Made up of radio, micro, infrared, visible light, ultraviolet, X-rays, and gamma raysVisible light makes up only a small portionCan be separated into its constituent colors by using a prism.
12 Atomic SpectraEmission Spectra (also referred to as bright line spectra) are the frequencies of light emitted by an element separated into discrete linesContinuous Spectrum is all wavelengths within a given range (usually applied to ROYGBIV)Absorption Spectra are discreet energies absorbed from the continuous spectrum by electrons of a specific element
14 Recap…When atoms absorb energy, electrons move into higher energy levelsAtoms emit energy when they return to lower energy levels, sometimes in the form of lightAtomic emission spectrum – the frequencies of light emitted by an element separated into discrete linesEmission spectrums are the “fingerprint” of an atom
15 Louis de Brolglie predicted that light can behave as a wave as well as a particle. Known as the Wave-Particle Duality TheoryThe Photoelectric Effect occurs when electrons are released from a metal when light is shone on it.This only occurs with certain frequencies of light.
16 Max Planck and Albert Einstein ( ) demonstrated that light behaves as if it were composed of tiny “packets” of energy called QUANTA or PHOTONSEnergy of a photon (absorbed or emitted) is proportional to the frequency of light
17 We can represent this relationship with an equation! E = hfh is known as Planck’s constant.h = 6.63x10-34J sQ: What type of relationship exists between energy and frequency?A: Direct
18 Try these…Calculate the frequency of a photon with energy 4.55x10-23 J.E = hff = E/hf = x10-23 J6.63x10-34 J sf = 6.86x1010 Hz
19 Calculate the energy of a photon whose frequency is 3.20x1011s-1 Answer…2.12x10-22J
20 Inadequacies of Bohr’s Model Much like the other models of the atom Bohr’s model had many weaknessesCould only explain the spectra of single atoms with one electronCould not explain why some emission lines are brighter than others
21 As we mentioned before… The quantum mechanical modelElectron clouds house electrons 90% of the timeBased on Schrödinger's equationsWerner Heisenberg also contributed to the Quantum mechanical model
22 Heisenberg was the head of the German Nuclear Energy Project under the Nazi regime. Heisenberg Uncertainty Principle states that its impossible determine velocity and position of an electron.Epitaph reads,“He lies somewhere here”