2Light Is a WaveAmplitude is the height of the wave from zero to the crest or from zero to the trough
3Wavelength 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
4Frequency 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
5The 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
6Try 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!
7Calculate 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
8What is the wavelength of radiation with a frequency of 1.50 x 1013 Hz? Answer…2.00 x 10-5m
9What frequency is radiation with a wavelength of 5.00 x 10-8m? Answer…6.00x1015 Hz
10The 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.
12Atomic 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
14Recap…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
15Louis 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.
16Max 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
17We 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
18Try 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
19Calculate the energy of a photon whose frequency is 3.20x1011s-1 Answer…2.12x10-22J
20Inadequacies 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
21As 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
22Heisenberg 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”