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# W PPT Update

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### W PPT Update

1. 1. Warm Up Stand up paddle boards (SUP’s) were first used by pacific islanders to travel between nearby islands. Why bother with paddling? Why not just surf waves the whole way across like a rad surfer dude?
2. 2. Defining Waves  Wave: A repeating disturbance (vibration) that moves through a medium carrying energy from one location to another.  Medium: a substance or material that carries the wave. A Wave Transports Energy and Not Matter
3. 3. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? NOT A WAVE
4. 4. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? WAVE
5. 5. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? NOT A WAVE
6. 6. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? WAVE
7. 7. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? WAVE
8. 8. Quick Quiz: Would this be a wave?  Is there an initial disturbance, or energy input?  Is energy transported from one point to another by a repeating vibration?  Is there a transport medium?  Is the energy transported through the medium, with the medium itself returning to it’s original position? WAVE?
9. 9. The Great Debate Isaac Newton: Light energy is carried as a packet of energy. Christiaan Huygens: Light energy is carried as a wave. Then along came Thomas Young
10. 10. Technically you’re both right…
11. 11. So what is the “medium” for light? Light does not have a physical medium. Rather than traveling through a solid, liquid, or gas – light is actually a disturbance in the Universe’s Electromagnetic Field!
12. 12. What is the Electromagnetic Field? • The electromagnetic field is invisible and can’t be “felt” the way a physical (solid, liquid, or gas) medium can. • The electromagnetic field extends indefinitely (without end) throughout space and across the universe. • It is a combination of electric and magnetic fields created by charged particles. If we can’t see it or feel it (in the conventional sense) how do we know it’s there? • Aurora Borealis • Static Electricity • Magnetic Compasses
13. 13. Classifying Waves
14. 14. How are WAVES classified? Waves can be classified by what they move through or by how energy moves through them.
15. 15. Classification of Waves By What They Move Through
16. 16. There are two classifications for waves based on what they move through: • Mechanical Waves • Electromagnetic Waves
17. 17. Mechanical Waves Mechanical Waves: Mechanical waves are waves that can only move through a physical medium.  Physical Mediums are made up of matter and take the form of solids, liquids, or gases. Examples:  Water Waves  Earthquake or Seismic waves  Sound Waves  Rope or Slinky Waves  Stadium Waves Remember that all these waves require a physical transport medium. Without matter (in a vacuum) they aren’t able to work.  Vacuum: Refers to empty space. Space that is not filled with matter in any form.
18. 18. Electromagnetic Waves Electromagnetic Waves: Electromagnetic waves are waves that do not require a physical transport medium. They travel along the universes electromagnetic field.  In other words they can travel through a vacuum.  Electromagnetic waves can also still pass through physical mediums. They just don’t depend on them. Examples:  Radio Waves  Microwaves  Infrared Waves  Visible Light  Ultraviolet Rays  X-Rays
19. 19. Classifying Waves By HOW Energy Moves Through Them
20. 20. There are three classifications for mechanical waves based on how energy moves through them: Transverse Waves Longitudinal Waves Surface Waves
21. 21. Transverse Waves Transverse Waves: Waves in in which the the medium vibrates perpendicular (at right angles to) the direction the wave travels. Examples: Waves in a Rope, Vibrating Guitar String, Light Waves (Special Type)
22. 22. LONGITUDINAL WAVES Longitudinal Waves: Waves in which the vibration (or disturbance) is parallel to the direction of the motion of the wave. Examples: Sound Waves
23. 23. Surface Waves Surface Waves: Waves that travel along the surface separating two different mediums. - Particle motion is circular. Examples: Water Waves
24. 24. Real World Connection: Earthquakes What type of waves do earthquakes produce? Answer: All Three!
25. 25. Real World Connection: Earthquakes  Primary Waves: The Primary or P Waves of an earthquake travel the fastest and are the first to be felt. They are longitudinal.  Secondary Waves: The secondary or S waves of an earthquake radiate out more slowly and arrive several seconds after the P Waves. They are transverse.  Rayleigh Surface Waves: These are the last waves to arrive and are accompanied by the largest up and down and side to side motion. They are responsible for the majority of destruction and damage. They are Surface Waves.
26. 26. Warm Up: Which wave is Transverse and which is Longitudinal? Wave A Wave B
27. 27. Check For Understanding A transverse wave is transporting energy from East to West. The particles of the medium will move_____. A) East to West only B) Both Eastward and Westward C) North to South only D) Both Northward and Southward
28. 28. Check For Understanding A wave is transporting energy from left to right. The particles of the medium are moving back and forth in a leftward and rightward direction. This type of wave is known as a ____. A) Mechanical B) Electromagnetic C) Transverse D) Longitudinal
29. 29. Check For Understanding You go to Comic-Con to get your picture taken with Batman. While waiting in line you decide to be the cool guy who starts a crowd wave. Is this wave transverse or longitudinal?
30. 30. Check For Understanding Why would you be far less popular if you attempted to start a longitudinal crowd wave instead?
31. 31. Check For Understanding A sound wave is a mechanical wave, not an electromagnetic wave. This means that: A) Particles of the medium move perpendicular to the direction of energy transport. B) A sound wave transports its energy through a vacuum. C) A physical medium is required in order for sound waves to transport energy. D) All of the above.
32. 32. Check For Understanding A science fiction film depicts inhabitants of one spaceship (in outer space) hearing the sound of a nearby spaceship as it zooms past at high speeds. Critique the physics of this film.
33. 33. Check For Understanding A transverse wave is transporting energy from East to West. The particles of the medium will move_____. A) East to West only B) Both Eastward and Westward C) North to South only D) Both Northward and Southward Correct Answer: D The particles would be moving back and forth in a direction perpendicular to energy transport. The waves are moving westward, so the particles move northward and southward.
34. 34. Check For Understanding A wave is transporting energy from left to right. The particles of the medium are moving back and forth in a leftward and rightward direction. This type of wave is known as a ____. A) Mechanical B) Electromagnetic C) Transverse D) Longitudinal Correct Answer: D The particles are moving parallel to the direction that the wave is moving. This must be a longitudinal wave.
35. 35. Check For Understanding You go to Comic-Con to get your picture taken with Batman. While waiting in line you decide to be the cool guy who starts a crowd wave. Is this wave transverse or longitudinal? Wave Direction Answer: Transverse
36. 36. Check For Understanding Why would you be far less popular if you attempted to start a longitudinal crowd wave instead? Correct Answer: Wave Direction
37. 37. Ouch! Ouch! Ouch! I hope Batman hits you with a Bat-A-Rang… in the face/
38. 38. Check For Understanding A sound wave is a mechanical wave, not an electromagnetic wave. This means that: A) Particles of the medium move perpendicular to the direction of energy transport. B) A sound wave transports its energy through a vacuum. C) A physical medium is required in order for sound waves to transport energy. D) All of the above. Correct Answer: C Mechanical waves require a physical medium in order to transport energy. Sound, like any mechanical wave, cannot travel through a vacuum.
39. 39. Check For Understanding A science fiction film depicts inhabitants of one spaceship (in outer space) hearing the sound of a nearby spaceship as it zooms past at high speeds. Critique the physics of this film. Correct Answer: This is an example of faulty physics in film. Sound is a mechanical wave and could never be transmitted through the vacuum of outer space.
40. 40. Anatomy of a Wave
41. 41. Crests, Troughs, and Cycles  Cycle: Single repeating unit of a wave. Waves are made up of many cycles.  Crest: The high point of a wave cycle.  Trough: The low point of a wave cycle.
42. 42. Wavelength (λ) and Amplitude Wavelength: The distance between any point on a wave and the equivalent point on the next cycle.  Generally expressed as the distance from crest to crest or trough to trough.  Basically the length (distance) of one cycle. Amplitude: The maximum distance the wave rises above the rest position (or drops below).  In other words the height of a crest or depth of a trough. @ Rest
43. 43. Period  Period: How much time it takes for a wave to complete one full cycle.  Units are always in terms of time (seconds).  The faster a wave moves, its wave period becomes smaller.  If you stood at a fixed point (like the oil rig). You could by measure the period of the waves starting your watch as a peak was passing by you and timing how long it took for the next peak to arrive.
44. 44. Frequency  Frequency is a measurement of how often a recurring event, such as a wave, occurs in a measured amount of time.  Frequency is a term you may already be familiar with.  How frequently do you clean your room?  You might respond: I clean my room 1 time per week or 2 times per year (Yuck!).  Frequency: How many cycles a wave makes in a given period of time.  Hertz: The unit used for frequency. Means one wave cycle per Second.  If a wave has a frequency of 500 Hz. How many cycles per second are there?
45. 45. Period vs. Frequency Period is how many seconds go by in 1 cycle. Frequency is how many cycles happen in 1 second. Period and Frequency are closely related but they are NOT the same thing!
46. 46. Which wave has a higher frequency? Answer: Blue Time
47. 47. The Relationship Between Frequency and Wavelength  Frequency is basically the number of cycles in a second.  Wavelength is the length (distance) of one cycle, usually in some form of meters. Therefore if you combine these units you get: Cycle Second Cycle Meters Meters Second Otherwise known as Speed
48. 48. Speed is a Constant The Speed of a wave depends only on the type of wave and the medium.  Light = 299,792,458 m/s  Sound = 340.29 m/s Therefore Frequency and Wavelength must be interrelated:  As wavelength increases, frequency must decrease.  As wavelength decreases, frequency must increase.
49. 49. But what about longitudinal waves?
50. 50. Sound Waves are a little different… Compression: When the medium (molecules) are forced, or pressed, together. Rarefaction: is just the opposite, it occurs when molecules are given extra space and allowed to expand.
51. 51. However for mathematical analysis it’s often easier to just draw sound waves as “transverse” with compressions corresponding to peaks and rarefactions to troughs.
52. 52. Why should you care about wave anatomy? The anatomy of a wave tells you how much energy the wave is carrying!
53. 53. Amplitude  Amplitude tells you the how much energy the wave is carrying.  Large Amplitude = High Energy  Small Amplitude = Low Energy  For light the amplitude of the wave tells you how bright the light will be.  For sound the amplitude of the wave tells you how loud the sound will be.
54. 54. Frequency / Wavelength Remember! Frequency and wavelength have an indirect relationship (as one goes up the other has to go down).  Frequency also corresponds to energy.  High Frequency (Short Wavelength) waves carry more energy.  Low Frequency (Long Wavelength) wave carry less energy.  For light the frequency / wavelength of the wave tells you what color the light will be.  High Frequency (Short Waves) = Violet Light (For Visible Light)  Low Frequency (Long Waves) = Red Light (For Visible Light)  For sound the frequency / wavelength of the wave tells you what pitch the sound will have.  High Frequency (Short Waves) = High Notes  Low Frequency (Long Waves) = Low Notes
55. 55. High Frequency and Short Wavelengths Low Frequency and Long Wavelengths
56. 56. How to Remember the Energy Difference Between Radio Waves and Gamma Rays… VS.