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Daily Work Organizer

Daily Work Organizer. Constructive or Destructive interference?. Homework : Pre-Lab pg 204-208. Vocab. Constructive Interference. Occurs at any location along the medium where the two interfering waves have a displacement in the same direction. Can create Maxima Build

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Daily Work Organizer

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  1. Daily Work Organizer Constructive or Destructive interference? Homework: Pre-Lab pg 204-208

  2. Vocab Constructive Interference • Occurs at any location along the medium where the two interfering waves have a displacement in the same direction. • Can create Maxima • Build • Amplitudes add together Constructive interference between 2 waves can create maxima or antinodes.

  3. Vocab Destructive Interference • “Minima” • Destroy • Amplitudes subtract • Resulting wave is smaller • Occurs at any location where two interfering waves have amplitudes in opposite directions.

  4. New Tardy Policy • If you’re tardy, more than once in a week, you lose 2 points from your grade.

  5. Wave Phenomena It’s what we see…

  6. Wave Interference • Two wave sources near each other will create an interference pattern • Lines made from constructive interference are called antinodes or maxima • Lines made from destructive interference are called nodes or minima (no waves)

  7. What does it look like?

  8. Constructive Interference • Sourcesin phase • On some lines there are parts where crests overlap crests • Waves are out of step by one wavelength 3 4 2 3 1 S1 2 let’s count the difference in wavelengths 1 S2

  9. Destructive Interference • Sourcesin phase • On other lines crests overlap troughs • Waves are out of step by one half wavelength 2.5 2 3 1 S1 2 let’s count the difference in wavelengths 1 S2

  10. Interference • counting waves on the interference pattern

  11. Interference • counting waves on the interference pattern

  12. 2 minutes • Answer the questions on your Cornell notes!

  13. A & B 1. At which of the labeled point(s) would constructive interference occur? 2. How many of the six labeled points represent anti-nodes? 2

  14. Lets Start the Pre-Lab! ~ 5 minutes

  15. The purpose of this lab is to recognize constructive and destructive wave interference patterns and use these patterns to calculate the wavelength of the waves causing this pattern • Purpose of lab: to _______________ • Hypothesis: what do you expect to see and why? When a crest and trough of two waves overlap I expect to see: When the crests of two waves overlap I expect to see: Destructive interference => nodes Constructive interference => antinodes

  16. Hypothesis: what do you expect to see and why? When the distance between the 2 sources of waves increases I expect the distance between the nodes to ____________ because… When the wavelength increases I expect the distance between the nodes to ____________ because…

  17. To Part I of the lab! pg. 204

  18. Calculating wavelength • Wavelength can be calculated from measurements on a point on an antinode λ

  19. Calculating wavelength • L= length from point to midpoint between sources • x= perpendicular distance from point to central antinode • d= distance between sources • m= antinodenumber • (central is m=0)

  20. Calculating wavelength • Wavelength can be calculated with the formula • note: • or: • we can rewrite eqn as:

  21. Which this in mind… find the wavelength of a wave! pg 207 Answer the questions on pg 210 when you finish

  22. Which this in mind… find the wavelength of the wave in question 1pg 210 Continue onto question 2 and 3 when you finish

  23. To Part II of the lab! pg. 207

  24. Changing d • let’s look at the effect of changing the distance between the sources: d

  25. Changing d • let’s look at the effect of changing the distance between the sources: d • An increase in d makes nodes closer together

  26. Constructive Interference

  27. Changing wavelength • let’s look at the effect of changing the wavelength • note: larger λ means slower f

  28. Diffraction • Particles are blocked by barriers • But waves can bend around the edges

  29. Diffraction • Effects of wavelength and slit size • Larger wavelength means more diffraction • Larger slit size means less curve

  30. Diffraction • Compare UHF (smaller) to VHF (larger) TV waves • UHF waves slightly diffract below roof

  31. Diffraction • Compare UHF (smaller) to VHF (larger) TV waves • VHF waves diffract much more would this house get all the channels?

  32. Diffraction • Which direction are the waves flowing?

  33. Light Diffraction • Newton originally thought light was a particle • Thomas Young challenged the idea • He used diffraction to test for light being a wave • Two slits created an interference pattern

  34. Light Diffraction • This interference pattern can displayed on a screen • The diffraction pattern is seen as fringes • Dark spots are nodes, bright spots are antinodes

  35. Light Diffraction • Changing d and wavelength affect this pattern the same as they had the full interference pattern • Proof that light is a wave

  36. Diffraction • All waves can bend around edges

  37. Thin Film Interference • Each edge of a film can also be a wave source

  38. Thin Film Interference • When light hits a thin film… • some light reflects off surface… thin film

  39. Thin Film Interference • Some light refracts through… • then reflects off bottom surface thin film

  40. Thin Film Interference • These two rays then interfere with each other • Closed ended reflections thin film

  41. Thin Film Interference • The phase change determines the type of interference • Thin film interference equations • creating or blocking colors • example

  42. Time to practice Go to pg. 222

  43. Polarized Light • Light is a transverse wave • The wave below shows how this would appear • If we looked at this wave head on it would appear as a line going up and down

  44. Visualizing Polarized Light • Light is a transverse wave • The wave below shows how this would appear • If we looked at this wave head on it would appear as a line going up and down

  45. Unpolarized Light • Naturally occurring light has waves on all planes • This type of light is called unpolarizedlight

  46. Polarized Light • Naturally occurring light has waves on all planes • This type of light is called unpolarizedlight • Polarized light is made of waves vibrating only on one plane

  47. Drawing Polarized Light • Let’s imagine unpolarized light in just two planes of vibration • Vertical wave drawn as an arrow • Horizontal wave drawn as a dot

  48. 3 Methods of Polarization • Selective Absorption • Reflection • Double Refraction

  49. Selective Absorption • A film of molecules stretched out in same direction • These molecules absorb all the light in that plane • Remaining 50% (perpendicular to molecules) passes through • 2 filters lined up 90° to each other block 100%

  50. Reflection method: Glare! • The horizontal component of light tends to reflect off transparent surfaces (glare) • The vertical component of light tends to refract • Not a perfect polarization

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