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Light Intro!

Light Intro!. Light Intro!. Light Discussion Questions. What is light? Is light matter? Are there different kinds of light? If so, what are they? What is the same about those kinds of light? What is the difference between those kinds of light?

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Light Intro!

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  1. Light Intro!

  2. Light Intro!

  3. Light Discussion Questions • What is light? • Is light matter? • Are there different kinds of light? If so, what are they? • What is the same about those kinds of light? What is the difference between those kinds of light? • You may have heard about light waves. What other waves do you know about? • What do all these waves have in common? What is different about them? • You may have heard of the speed of light; It’s pretty darned fast. Do different kinds of light travel at the same speed or different speeds? • What are some questions about light that you have? List them on your index card.

  4. Visible part of EM SPectrum Waves 1/33,000” long Ray of White Light Waves 1/70,000” long Slit PRISM 400 nm – 700 nm Red Orange Yellow Green Blue Indigo Violet

  5. IMPORTANT LIGHT EQUATION #1 Frequency & wavelength are inversely proportional c =  c: speed of light (2.998  108 m/s) : wavelength (m, nm, etc.) : frequency (Hz or s-1) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  6. What wavelength of light has a frequency of 5.4 x 106 Hz? What type of light is it?

  7. 2) What frequencyof light has a wavelength of 2.2m? What type of light is it?

  8. 3) What frequency of light has a wavelength of 7.0 x 10-7m? What type of light is it? 4) What wavelength of light has a frequency of 9.7 x 1015Hz? What type of light is it?

  9. Let’s talk about Energy • Activity break 

  10. IMPORTANT LIGHT EQUATION #2 E: energy (J, joules) h: Planck’s constant (6.6262  10-34 J·s) : frequency (Hz) • The energy of a photon is proportional to its frequency. E = h Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  11. Electromagnetic Radiation=PHOTONS  Light as a wave Light as a stream of energy (packets of photons) Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 325

  12. Red and Blue Light Photons - particle of light that carries a quantum of energy Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 325

  13. What is the energy of a light wave with a frequency of 4.03 x 1011 Hz? What type of light is it?

  14. 2) What is the frequency of a light wave with an energy of 6.0 x 10-11 J? What type of light is it?

  15. What is the frequency of a light wave with an energy of 1.33 x 10-20 J? What type of light is it?

  16. Today is Monday, 3/18 • Light Equations 1 & 2 • Trade & Talk • x2 examples of combined Light Equations • Tomorrow’s info • Photons!! • Absorption / Emission

  17. I CAN… • solve for any variable in the combined light equation • Explain how light acts as a particle (photon) and also has wave properties • explain how we perceive frequency and amplitude • understand how energy is absorbed and emitted as light • identify different frequency types of light

  18. Example problem using BOTH Equations… Find the energy of a photon with a wavelength of 1.0 x 10-3 nm. c = λv E = hv • GIVEN: h = 6.626 x 10-34 J s c = 3.00 x 108 m/s • = ? • E = ? = 1.0 x 10-3 nm = ???? m WORK:  = c   = 3.00  108 m/s 1.0 x 10-12 m = 3.0 x 1020 s-1 E= (6.626 x 10-34 J s)(3.0 x 1020s-1) E = 2.0x 10-13 J

  19. Example problem using BOTH Equations… Find the wavelength of a photon with an energy of ：6.2x 10-10 J. c = λv E = hv WORK:  = c  • GIVEN: h = 6.626 x 10-34 J s c = 2.998 x 108 m/s  = ? • = ? • E = 6.2 x 10-10 J  = 6.2 x 10-10 J 6.626 x 10-34m  = 9.356 x 1023 s-1 λ = 2.998 x 108 m/s 9.356 x 1023 s-1 λ = 3.20 x 10-16 m

  20. Energy of Waves – It takes more energy to travel at a higher frequency… Amplitude Low frequency Low frequency, long wavelength short wavelength l Amplitude High frequency, short wavelength

  21. Electromagnetic Radiation=PHOTONS  Light as a wave Light as a stream of energy (packets of photons) Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 325

  22. Vocabulary of a Wave Frequency (Hz or s-1) ? l Wavelength (m or nm) A Amplitude (m) c = speed of light = 2.998 x 10 8 m/s (really fast, true for every kind of light!) Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 324

  23. Photons • Amplitude – The ‘height’ of a wave; We perceive it as intensity • Photon • a particle light that carries a quantum of energy with the lowest detectable amplitude • More photons means more intensity! • Different photons have different energies

  24. Red and Blue Light Photons - particle of light that carries a quantum of energy Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 325

  25. Absorption / Emission • Energy absorption – Energy is absorbed into an atom, exciting an electron from a lower energy level to a higher energy level • Energy emission – Energy is released as a light photon when the electron relaxes back to it’s ground state (or lowest energy level) • Bohr model of the atom explains how this works

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

  27. e- e- e- e- e- e- e- e- e- e- Bohr Model of Atom n = 3 Increasing energy of orbits n = 2 n = 1 The Bohr model of the atom, like many ideas in the history of science, was at first prompted by and later partially disproved by experimentation. e- A photon is emitted with energy E = hv http://en.wikipedia.org/wiki/Category:Chemistry

  28. Continuous vs. Quantized Energy Energy White light   Colored light A B continuous quantized Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 330

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  30. Pre-Lab! • Flame test lab tomorrow • You will be testing the type of light emission for different metal cations • It’s super fun! • Then you will quantify (code for calculate..) the emissions!

  31. Types of A / E • Types of energy absorption: • Electricity (electric energy) • Photons (light energy) • Infrared (heat energy) • Some types of light energy emission: • Fluoresence via UV absorption (demo) • Infrared (demo) • Visible – different colors (demo) • Incandescenct lights (demo) • Fluoresenct lights

  32. Types of absorption • Electric energy – electricity, this is how your light bulbs get the energy to emit light energy in the form of photons • Infrared energy – heat, this is how you will get the metal cations in lab tomorrow to emit light energy • Photons – light energy can be absorbed and immediately emitted by materials to be perceived as a certain color • For example, my green shirt absorbs all types of photons but green photons, it immediately re-emits and therefore you and I perceive the shirt to be green

  33. Types of Emission • Fluoresence– fluoresence happens when an atom absorbs a high energy light photon and emits a lower energy photon • i.e. When UV light is absorbed and visible light is emitted! • Infrared – heat lamp emits both infrared photons and visible light photons, which has higher energy? • Visible – Many metal cations absorb and emit visible light photons • What about the ones that don’t, are they emitting anything?

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