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Waves Chemistry Mrs. Coyle

Waves Chemistry Mrs. Coyle

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Waves Chemistry Mrs. Coyle

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  1. WavesChemistryMrs. Coyle

  2. Wave • Wave: a rythmic disturbance in both time and space. • Waves transfer energy not matter.

  3. Amplitude: The distance from the equilibrium (baseline) to the crest or trough) l

  4. Wavelength: The distance from the crest to crest or trough to trough. l

  5. Frequency: the number of waves per second (Hertz, Hz) l

  6. Low amplitude - High amplitude

  7. Speed of a Wave v =lf v speed l wavelength f frequency

  8. Speed of a Wave v= d/t v = l/T v =lf

  9. Transverse Waves The particles vibrate perpendicular to the direction of the wave's propagation (ex: waves along a string, electromagnetic waves).

  10. Longitudinal Waves • The particle displacement is parallel to the direction of wave propagation (ex: sound)

  11. Elliptical Waves Result when longitudinal and transverse waves are superpositioned. (ex: surface water waves)

  12. Torsional Waves • Video link on Web • http://www.youtube.com/watch?v=P0Fi1VcbpAI

  13. Wave Categories • MechanicalWaves: require a medium. Examples: • Water waves( Tsunami) • Sound waves (f=20-20000 hertz, v= 340 m/sec in air but varies for different media, faster in solids) • Earthquake waves • ElectromagneticWaves: do not require a medium. Can travel through space (vacuum). Example: Light from the sun reaches us Note: all EM waves have a speed through vacuum of 3 x 108 m/sec.

  14. Electromagnetic Waves Type of radiation Wavelengths(m) Radio 570 - 2.8 TV 5.6 - 0.34 Microwave 0.1 - 0.001 Infrared radiation 10-3 - 10-7 visible light red 700x10-9 (700nm) orange yellow green blue indigo violet 400x10-9 (400nm) ultraviolet 10-7 - 10-10 x-rays 10-10 -10-12 gamma rays shorter than 10-12

  15. Note • A wave’s speed is constant in a given medium. If you change the frequency of the wave, the wavelength will also change. If the frequency increases, the wavelength will decrease. • When a wave travels from one medium to a different medium, the frequency remains the same and the speed changes.

  16. Problem • What is the frequency of a light wave of wave length 550x 10-9 m? • What color light is it?

  17. Refraction

  18. Dispersion

  19. Diffraction

  20. Remember my atomic model?

  21. Electrons orbit the nucleus in circular paths of fixed energy (energy levels). Niels Bohr’s Atomic Model (1913)

  22. Niels Bohr’s Atom Cont’d • Electrons can jump from energy level to energy level. • Electrons absorb or emit light energy when they jump from one energy level to another.

  23. Hydrogen Emission Spectrum Violet 410nm Blue 434nm Blue-Green 486 nm Red 656nm Balmer Series

  24. Bohr Model for Hydrogen