Formation of Light Nucleus e e Lithium Atom + Ground State e e Excited State e Electron Returns to Ground State Light is given off e Ion is formed Li  e + Li 1+ hv n = 1 n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 Nucleus

Waves Wavelength ( ) - length of one complete wave Frequency ( ) - # of waves that pass a point during a certain time period –hertz (Hz) = 1/s Amplitude (A) - distance from the origin to the trough or crest Courtesy Christy Johannesson f

The Electromagnetic Spectrum AM radio Short wave radio Television channels FM radio Radar Microwave Radio Waves Gamma Rays X- Raysinfrared Increasing photon energy Increasing frequency Decreasing wavelength Red Orange Yellow Green Blue Indigo Violet UV Rays VisibleLightVisibleLight R O Y G B I V HIGHENERGYHIGHENERGY LOWENERGYLOWENERGY

Frequency O’Connor, Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles  1982, page second Frequency 4 cycles/second = 4 hertz 12 cycles/second = 12 hertz 36 cycles/second = 36 hertz

AM & FM Waves Carrier frequency Sound pattern Amplitude Modulated carrier Frequency Modulated carrier AM - FM Radio

Electromagnetic Spectrum LOWENERGYLOWENERGY HIGHENERGYHIGHENERGY  rays X-raysUltravioletInfraredMicrowave Radar Radio waves TV FM Short Wave Long Wave Visible spectrum nm nm 10 0 nm10 1 nm10 2 nm cm cm cm 10 0 cm 10 1 cm 1cm 10 1 m10 2 m10 3 m 10 4 m Hz10 18 Hz10 17 Hz Hz Hz10 13 Hz Hz Hz10 10 Hz10 9 Hz 100 MHz 10 MHz1 MHz100 KHz RedOrangeYellowVioletBlueGreen 700 nm 600 nm 500 nm400 nm Wavelength, Frequency, 10 3 nm Hz Electromagnetic spectrum White Light Davis, Frey, Sarquis, Sarquis, Modern Chemistry  2006, page 98

Waves Low frequency High frequency Amplitude long wavelength  short wavelength 

Waves Low frequency High frequency Amplitude long wavelength  short wavelength  60 photons 162 photons low energy high energy

Electromagnetic Radiation Light as a wave Light as a stream of energy (packets of photons) Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 325

Wavelength and Frequency E = h c =  c = speed of light (3 x 10 8 m/s) = frequency (s -1 )  = wavelength (m) E = energy (Joules or J) h  = Planck’s constant (6.6 x J/s) = frequency (s -1 ) f f f f “nu” “lambda”

Electromagnetic Spectrum GIVEN: f = ? = 434 nm = 4.34  m c = 3.00  10 8 m/s WORK: f = 3.00  10 8 m/s 4.34  m f = 6.91  Hz EX: Find the frequency of a photon with a wavelength of 434 nm. Courtesy Christy Johannesson 1 x 10 9 nm 1 m

Coins are Quantified Do we have a coin for 37cents? Light is also quantified and only comes in certain bundles called photons.

Bohr Model of Hydrogen Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 331 Nucleus Possible electron orbits e e

Continuous vs. Quantized Energy Energy A B Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 330 continuous quantized

Continuous vs. Quantized ABAB Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 330

Wavelength and Frequency E = h c =  c = speed of light (3 x 10 8 m/s) = frequency (s -1 )  = wavelength (m) E = energy (Joules or J) h  = Planck’s constant (6.6 x J/s) = frequency (s -1 ) f f f f “nu” “lambda”

Photoelectric Effect No electrons are emitted Electrons are emitted Metal plate Bright red light infrared rays or Dim blue light ultraviolet rays or

Intensity of Radiation 1x 2x 3x ¼ light 1 / 9 light Light intensity = 1/(distance) 2

The Photoelectric Effect When light strikes a metal surface, electrons are ejected. If the threshold frequency has been reached, increasing the intensity only increases the number of electrons ejected. If the frequency is increased, the Ejected electrons will travel faster. A B C Light Electron Metal Nucleus More Light Electron Metal Nucleus Electron Higher frequency light Faster electron Metal Nucleus

Photoelectric Effect Some key results For low frequency light (low energy, below threshold) - electrons are not ejected regardless of the light’s intensity (number of light waves) For high frequency light (high energy, above threshold) - same number of electrons are ejected regardless of the frequency (energy of light waves) - Increasing the light’s intensity increases the number of electrons ejected (increases the current) Einstein considered light as mass-less, energetic particles (photons) to help explain this effect – energy follows Planck’s equation.

Photoelectric Generator Solar Calculator

The Photoelectric effect and the frequency of light IR, infrared R ed O range Y ellow G reen B lue V iolet UV, ultraviolet UV v b g y o r IR Lens Slit Quartz prism Light source Hill, Petrucci, General Chemistry An Integrated Approach  1999, page 292 Potassium

Quantum Theory E:energy (J, joules) h:Planck’s constant (  J·s) :frequency (Hz) E = h The energy of a photon is proportional to its frequency. Courtesy Christy Johannesson

Quantum Theory GIVEN: E = ? = 4.57  Hz h =  J· s WORK: E = h E = (  J· s ) ( 4.57  Hz ) E = 3.03  J Example: Find the energy of a red photon with a frequency of 4.57  Hz. Courtesy Christy Johannesson

Color = Energy of Photons Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 329

Energy Level Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 329 A B CD Ground state Energy Four excited states

An Excited Lithium Atom Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 326 Photon of red light emitted Li atom in lower energy state Excited Li atom Energy

Frequency A Frequency B Frequency C n = 2 n = 1 n = 3 A B C A + B = C

Bohr’s Experiment Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 76 Animation by Raymond Chang – All rights reserved.

Hydrogen Spectral Lines Lyman series (ultraviolet) Balmer series (visible) Paschen series (infrared) Frequency (hertz) n =

Hydrogen Spectral Lines A B C D E F Lyman series (UV) A B C D E Balmer (Visible) A B C D Paschen (IR) E1E1 E2E2 E3E3 E4E4 E5E5 E6E6 Energy Bohr’s model of the atom accounted mathematically for the energy of each of the transitions shown. IR region UV region 656 nm 486 nm 434 nm 410 nm Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 97 ionization

Continuous and Line Spectra 4000 A o light Na H Ca Hg nm Visible spectrum  (nm)

Flame Emission Spectra Photographs of flame tests of burning wooden splints soaked in different salts. Include link to web page methane gas wooden splintstrontium ioncopper ionsodium ion calcium ion

The Electromagnetic Spectrum AM radio Short wave radio Television channels FM radio Radar Microwave Radio Waves Gamma Rays X- Raysinfrared Increasing photon energy Increasing frequency Decreasing wavelength Red Orange Yellow Green Blue Indigo Violet UV Rays R O Y G B I V VisibleLightVisibleLight

Wavelength (nm) Absorbance Absorbance of Chlorophyll Frequency (Hz) Wavelength (nm) cosmic rays gamma rays x-raysultra- violet infra- red radio (microwave) radartele- vision radiopower transmission VioletBlueGreen YellowOrangeRed UV Near Infrared 400 nm 500 nm 600 nm 700 nm

Wave Interference

Bright

A B C D Waves crest trough wavelength amplitude E FG H reflection refraction total internal reflectiondiffraction crest wavelength amplitude trough reflection refraction diffraction total internal reflection (Match the terms…)

Polarizing Filter Vertical polarizing filter Horizontal polarizing filter Vertical wave passes through Horizontal wave is blocked side view Vertical wave is blocked by horizontal polarizing filter