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Section 5.1

Section 5.1. Light and Quantized Energy. Objectives. Compare the wave and particle models of light Define a quantum of energy and explain how it is related to an energy change of matter Contrast continuous electromagnetic spectra and atomic emission spectra. Light and Quantized Energy.

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Section 5.1

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  1. Section 5.1 Light and Quantized Energy

  2. Objectives • Compare the wave and particle models of light • Define a quantum of energy and explain how it is related to an energy change of matter • Contrast continuous electromagnetic spectra and atomic emission spectra

  3. Light and Quantized Energy • Wave Nature of Light • Electromagnetic radiation (ER)form of energy that exhibits wavelike behavior as it travels through space. • Exs: visible light, microwaves, x-rays

  4. Characteristics of waves • Wavelength, :shortest distance between equivalent points on a continuous wave. • Usually in nm • Frequency, : number of waves that pass a given point per second. • Hz (Hertz)

  5. Continued • Amplitude: wave’s height from the origin to a crest, or from the origin to a trough. • Speed of light = c = 3.0x108 m/s

  6. Light and Quantized Energy

  7. Electromagnetic Spectrum • Continuous spectrum of different types of ER. • No portion that does not correspond to a unique wavelength and frequency.

  8. Light and Quantized Energy

  9. Light and Quantized Energy • Calculating wavelength/frequency • Example P.121

  10. Particle Nature of Light • Besides having wave characteristics, light also acts like a particle. • The Quantum Concept: Energy can only be gained or lost in a specified amount  Quantum • Equantum = hν • h is Plank’s Constant = 6.626 x 10-34 J•s

  11. Blocks and Quanta • Think of energy transfer like building a wall of Legos®. • Only add/take away 1 Lego. • No ½ Lego.

  12. Photoelectric Effect • Electrons, called photoelectrons, emit from a metal’s surface when light of a certain frequency shines on the surface. Light Photoelectrons

  13. The Photon • Photon: • particle of electromagnetic radiation • no mass • carries a quantum of energy • Ephoton = hv

  14. Neon Signs

  15. Atomic Emission Spectra • Electricity passed through a tube of gas • Gas atoms absorb energy and become excited • Atoms release the energy absorbed as light.

  16. Atomic Emission Spectra Hydrogen (H) Helium (He) Oxygen (O) http://astro.u-strasbg.fr/~koppen/discharge/index.html

  17. Atomic Emission Spectra Neon (Ne) Xenon (Xe) http://astro.u-strasbg.fr/~koppen/discharge/index.html

  18. Example Problem 5-2 p. 124

  19. Homework • Wave and Energy Worksheet

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