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Daily Work OrganizerFridayQuestion of the Day: How does interference create Nodes and Antinodes?Do Now:

Agenda:Cornell notesPre-labHomeworkHomework:Pre-Lab pg 204-208

Constructive or Destructive interference?

VocabWordPicture that reminds you of definitionDefinitionWord or words that remind you of definitionSentence using word

Constructive InterferenceCan create MaximaBuild Amplitudes add togetherOccurs at any location along the medium where the two interfering waves have a displacement in the same direction.

Constructive interference between 2 waves can create maxima or antinodes.VocabWordPicture that reminds you of definitionDefinitionWord or words that remind you of definitionSentence using word

Destructive InterferenceMinimaDestroyAmplitudes subtractResulting wave is smallerOccurs at any location where two interfering waves have amplitudes in opposite directions.

New Tardy Policy If youre tardy, more than once in a week, you lose 2 points from your grade. Its what we seeWave Phenomena

5picture from http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Moire_on_parrot_feathers.jpg/800px-Moire_on_parrot_feathers.jpgWave InterferenceTwo 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)

6What does it look like?

Constructive InterferenceSources in phase On some lines there are parts where crests overlap crestsWaves are out of step by one wavelengthS1S21231234lets count the difference in wavelengths8

Destructive InterferenceSources in phase On other lines crests overlap troughsWaves are out of step by one half wavelengthS1S2122.5123lets count the difference in wavelengths9Interferencecounting waves on the interference pattern

10Interferencecounting waves on the interference pattern

112 minutesAnswer the questions on your Cornell notes!

1. At which of the labeled point(s) would constructive interference occur?

2. How many of the six labeled points represent anti-nodes?

A & B2Lets Start the Pre-Lab! ~ 5 minutesPurpose of lab: to _______________

Hypothesis: what do you expect to see and why?

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 patternWhen a crest and trough of two waves overlap I expect to see:

When the crests of two waves overlap I expect to see: Constructive interference => antinodesDestructive interference => nodesHypothesis: 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

To Part I of the lab!pg. 20417Calculating wavelength

Wavelength can be calculated from measurements on a point on an antinode18Calculating wavelength

L= length from point to midpoint between sourcesx= perpendicular distance from point to central antinoded= distance between sourcesm= antinode number(central is m=0)19

Wavelength can be calculated with the formula

note:

or:

we can rewrite eqn as: Calculating wavelength

20Which this in mind find the wavelength of a wave!

pg 207

Answer the questions on pg 210 when you finishWhich this in mind find the wavelength of the wave in question 1

pg 210

Continue onto question 2 and 3 when you finishTo Part II of the lab!pg. 20723Changing dlets look at the effect of changing the distance between the sources: d

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Changing dlets look at the effect of changing the distance between the sources: dAn increase in d makes nodes closer together25Constructive Interference

26Changing wavelengthlets look at the effect of changing the wavelength

note: larger means slower f27DiffractionParticles are blocked by barriersBut waves can bend around the edges

28DiffractionEffects of wavelength and slit sizeLarger wavelength means more diffractionLarger slit size means less curve29DiffractionCompare UHF (smaller) to VHF (larger) TV wavesUHF waves slightly diffract below roof

30DiffractionCompare UHF (smaller) to VHF (larger) TV wavesVHF waves diffract much more

would this house get all the channels?31DiffractionWhich direction are the waves flowing?

32Light DiffractionNewton originally thought light was a particleThomas Young challenged the ideaHe used diffraction to test for light being a waveTwo slits created an interference pattern33Light Diffraction

This interference pattern can displayed on a screenThe diffraction pattern is seen as fringesDark spots are nodes, bright spots are antinodes34Light DiffractionChanging d and wavelength affect this pattern the same as they had the full interference pattern

Proof that light is a wave

35DiffractionAll waves can bend around edgesColor intervalinfrared>700 nmred635 700 nmorange590 635 nmyellow560 590 nmgreen490 560 nmblue450 490 nmviolet400 450 nmultraviolet