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SI Waves

SI Waves. 8 West SI.

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SI Waves

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  1. SI Waves 8 West SI

  2. We are learning to: demonstrate how waves transfer energy.We are looking for: a disturbance or variation that transfers energy from one point to another point in a medium. Transverse waves- wave and medium move in direction that is perpendicular to each other Longitudinal waves- wave and medium move in same direction

  3. What are Waves? • A wave is a disturbance that transfers energy from place to place • Waves travel through a material called a medium. • Waves that require a medium to travel through are called mechanical waves.

  4. What are Waves? • Waves are created when a source of energy causes a medium to vibrate. • A vibration is a repeated back-and-forth or up-and –down motion.

  5. Classification of Waves • Wave are classified according to how they move. • Types of waves: 1. Transverse 2. Longitudinal 3. Surface

  6. Transverse Wave • In transverse waves, the particles of the medium move perpendicular in the direction of the wave. • Parts of the transverse wave: • Crest • Trough • Wavelength • Amplitude

  7. Longitudinal Wave • In longitudinal waves, the particles of the wave move parallel to direction of the wave movement. • Parts of the wave: • Compressions • Rarefactions • Wavelength

  8. Surface Wave • Surface waves occur at the boundary between two mediums and are a combination of transverse and longitudinal waves.

  9. A transverse wave….. • Vibrates particles perpendicular to the direction of wave • Vibrates particles parallel to the direction of the wave • Vibrates both parallel and perpendicular to the direction of the wave • Vibrates particles in one direction • Help! I don’t understand. 0 of 5 10

  10. What type of wave is represented by picture? • Transverse • Longitudinal • Surface • Seismic • Help! I don’t understand. 0 of 5 10

  11. A wave is a disturbance that transfers • matter. • particles. • energy. • a medium. • Help! I don’t understand. 0 of 5 10

  12. What do you call the material that a wave travels through? • Plasma • Space • Vacuum • Medium • Help! I don’t understand. 0 of 5 10

  13. What type of wave is represented by the animation? • Longitudinal • Transverse • Surface • Seismic • Help! I don’t understand. 0 of 5 10

  14. Transverse Wave

  15. Longitudinal Wave

  16. We are learning to: describe the properties of waves.We are looking for: Wavelength-distance from crest to crest (transverse wave), or from compression to compression (longitudinal wave)Frequency-number of waves that pass a given point each secondAmplitude-distance from rest position to the crest (transverse wave); measures how compressed the particles of the medium are (longitudinal wave); determines the amount of energy of each wave

  17. Wave Properties(continued) • Wavelength is the distance from one crest to the crest of the next wave. • Period is the time required for one full wavelength of a wave to pass a certain point. • Frequency of a wave is the number of full wavelengths that pass a point in a given time interval.

  18. Wave Properties • Transverse waves have the shape of a sine curve. • Highest point of a transverse wave is a crest. • Lowest point of a transverse wave is a trough. • Amplitude is the greatest distance that particles are displaced from their normal resting position.

  19. Frequency-Period Equation • Frequency=1/period • F=1/T • Frequency is measured in a unit called a hertz.

  20. Wave Speed • wave speed=frequency x wavelength • v = f x λ

  21. In the diagram, identify the wave property “A” • Frequency • Amplitude • Wavelength • Help! I don’t understand. 0 of 5 10

  22. Which of the following is true about waves in the diagram? • Wave X has a higher frequency than Wave Y • Wave X has a lower frequency than Wave Y • Wave X has the same frequency as Wave Y • Help! I don’t understand. 0 of 5 10

  23. Which of the waves in the picture has the greatest amplitude? 1 2 • 1 • 2 • 3 • Help! I don’t understand. 3 0 of 5 10

  24. Which property measures the amount of energy transferred by a wave? • Wavelength • Frequency • Amplitude • Help! I don’t understand. 0 of 5 10

  25. ALIKE BUT DIFFERENT

  26. We are learning to demonstrate how waves transfer energy. We are looking for how waves interact with an object or other waves.  They either: Transmit-wave energy passes through an object. Reflect-wave energy bounces off an object. Refract – wave changes speed as it passes from one medium to another medium Diffract – wave spreads out as it passes through an opening or around the edge of a barrier Absorb-wave energy is taken in by an object they encounter. Interference-wave energy of multiple waves is combined.

  27. Reflection • Reflection is the bouncing back of a wave when it meets a surface or boundary.

  28. Diffraction • Diffraction is when a wave bends around an object or opening.

  29. Refraction • Refraction is the bending of a wave as it passes from one medium to another medium.

  30. Wave Interference • Wave interference is when several waves are in the same location and the waves combine to produce a single, new wave that is different from the original waves.

  31. Constructive Interference • The result of two individual waves coming together to produce a wave of greater amplitude is called constructive interference.

  32. Destructive Interference • The result of two individual waves coming together to produce a wave of lesser amplitude than the larger of the original waves is called destructive interference.

  33. What happens to the energy of the wave when the crest of the blue wave meets the crest of the green wave? • Energy decreases. • Energy increases. • Energy stays the same. • I don’t get it! Help! 0 of 5 10

  34. What is it called when a wave bounces off of a barrier? • Refraction • Reflection • Diffraction • Help! I don’t know. 0 of 5 10

  35. What happens to waves as they go through an opening or around a corner of an object? • They are refracted. • They are reflected. • They are diffracted. • Help! I don’t know. 0 of 5 10

  36. As waves go through different mediums, what happens to them? • Waves change speed and are reflected. • Waves change speed and are refracted. • Waves change speed and are diffracted. • Help! I don’t know. 0 of 5 10

  37. ALIKE BUT DIFFERENT Reflection, Refraction & Diffraction

  38. We are learning to: demonstrate that vibrations produce longitudinal waves which move away from the original source. We are looking for: an explanation of the following: A medium is required (mechanical wave) A sound is produced (acoustic energy) A vibration is required to produce sound waves (longitudinal wave)

  39. Sound • Sound waves are caused by vibrations, and carry energy through a medium. • Sound waves are longitudinal waves. • Speed of sound depends on the medium.

  40. Speed of Sound • Speed of sound at room temperature is about 346 m/s. • An increase in temperature increases the speed of sound. • Sound waves travel faster in liquids & solids than gases.

  41. Energy is required to create a sound wave. Sound energy is also known as . . . • Elastic potential energy • Radiant energy • Acoustic energy • Thermal energy • Help! I don’t understand. 0 of 5 10

  42. How does sound transfer energy? • By vibration of a medium, producing a transverse wave. • By vibration of a medium, producing a longitudinal wave. • By vibration of a medium, producing a surface wave. • Help! I don’t know. 0 of 5 10

  43. Sound cannot be heard in which of the following locations? • In a building • Under water • In space • In the forest • Help! I don’t know. 0 of 5 10

  44. FOUR BLOCK INTERVENTION INSTRUCTIONS • If you have not missed any questions, start with block #2 and then complete blocks #3 and #4. • If you have missed 2 or more, meet with the teacher. • Everyone else starts in block #1 and then complete blocks #2, #3, and #4.

  45. 1. PRACTICE 2. EXTENSION A tree falls in a forest and no one is around to hear it. Is a sound produced? Using your knowledge of sound waves, write a paragraph (6-10 sentences)explaining why or why not? Explain how a sound is produced when you beat a drum. 3. REVIEW 4. FRONTLOAD Draw a transverse wave and a longitudinal wave. Label all of their parts. What do you know about the electromagnetic spectrum?

  46. We are learning to: demonstrate that vibrations produce longitudinal waves which move away from the original source. We are looking for: the identification of the properties of sound. Intensity-how much energy sound has Loudness-our perception of intensity Pitch-frequency of waves produced (highness and lowness of sound) (i.e. Doppler Effect)

  47. Loudness determined by Intensity • Intensity of a sound wave describes the rate at which a sound wave transmits energy through a given area of the medium. • Loudness depends on the intensity of the sound wave. • The greater the intensity, the louder the sound.

  48. Relative Intensity • The relative intensity of sounds is found by comparing the intensity of a sound with the intensity of the quietest sound a person can hear. • Relative intensity is measured in units called decibels.

  49. Pitch • The pitch of a sound is related to the frequency of sound waves. • High pitch correspond to a high frequency, and low pitch corresponds to a low frequency.

  50. The Doppler Effect • The apparent change in frequency as a wave source moves in relation to the listener is called the Doppler Effect. • As sound source moves toward the listener, the waves reach the listener with a higher frequency. • The pitch appears to increase because of the Doppler effect.

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