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Waves

Learn about waves and their properties, including the two types of waves (mechanical and electromagnetic), transverse and longitudinal waves, and the characteristics of waves. Discover how waves transmit energy without transferring matter and explore the relationship between frequency, period, and wavelength. This informative resource provides a comprehensive overview of wave behavior and properties.

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Waves

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  1. Waves

  2. Waves and Wave Properties

  3. Why are we able to see? Answer: Because there is light. And…what is light? Answer: Light is a wave. So…what is a wave?

  4. Answer: A wave is a disturbance that carries energy from place to place. A wave does NOT carry matter with it! It just moves the matter as it goes through it.

  5. What are the two types of waves?

  6. Types of Waves: * Mechanical – require a medium (ex. water and sound) * Electromagnetic – Do not need medium (ex. Light, radio, x-rays)

  7. What are the two types of MECHANICAL waves?

  8. 2 main types of MECHANICAL waves: 1) Transverse • Longitudinal (Longitudinal is also called a Compressional wave)

  9. Other Wave Types • Earthquakes: combination • Ocean waves: surface • Light: electromagnetic

  10. Who can be the first group to demonstrate a transverse wave with your slinky?

  11. Volunteer to demonstrate / create a transverse wave?

  12. Transverse Waves • Oscillations are perpendicular to the direction the wave moves Ex: If the wave moves left to right Oscillation is up & down http://www.physicsclassroom.com/mmedia/waves/lw.html

  13. Using your whiteboard… Label the parts of a transverse wave. Pair to legibly label all parts earns tickets.

  14. Highs and Lows for a Transverse Wave • Crests: high point (Sometimes called wave fronts) • Troughs: low point

  15. Draw and label a transverse wave.(include crest, trough, wavelength and amplitude) http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html

  16. Wavelength (): • The length of one complete cycle of a wave • Any point on the wave to the next identical point (ex. Crest to crest, midpoint to midpoint, trough to trough) • Represented by the Greek letter “Lambda” Wavelength does NOT effect speed!

  17. WAVELENGTH(shortest distance between 2 points.)

  18. Amplitude: Maximum displacement from rest or equilibrium (Half the distance between highest and lowest points)

  19. Longitudinal Waves • Oscillations are in the samedirection as the wave moves • Ex: Longitudinal Wave in a Slinky • The compression will move along the slinky forward and then back.

  20. To create a wave, you create a _______________ at one end of the slinky. That _______________ then is transferred to the next coil, and the next, and so on. PULSE ENERGY

  21. LONGITUDINAL WAVE: particle displacement is parallel to the direction of wave propagation… Do the particles move or oscillate about their equilibrium (fixed point)? Pick a particle and try to follow it….

  22. Instead of crests & troughs, a longitudinal wave has compressions & rarefactions. * compression – a pulse of compressed air or other material - High Pressure area * rarefaction - less dense area - Low Pressure area in the air - stretched area of a spring

  23. Sound waves are Longitudinal But you can hear on other sides of the tuning fork….

  24. Longitudinal wave from a monopole source. radiates sound equally well in all directions.

  25. What about more than one source?Click Here to learn more

  26. Longitudinal Characteristics Crest Trough

  27. Identify as Longitudinal or Transverse Wave Longitudinal Transverse Longitudinal Transverse

  28. SURFACE WAVES • Mix both longitudinal and transverse waves

  29. A wave can transmit __________ without transferring matter? • The shortest distance between two points on a wave where the wave pattern is repeated is the ______________. ENERGY WAVELENGTH

  30. What causes the disturbance?2 ways to produce a wave: 1. Wave Pulse:single disturbance that travels through a medium. Ex. Rock thrown in pond 2. Traveling Wave: series of pulses at regular intervals Ex. 1. Moving rope side to side 2. Continuously ringing bells

  31. Measures of a Wave: • Waves have frequency, wavelength, and velocity (they are all related). Frequency: How often the wave goes up and down Measured in hertz (Hz)

  32. FREQUENCY (f)Unit (Hertz or cycles/ sec) • NUMBER OF VIBRATIONS (WAVES) THAT PASSES A FIXED LOCATION IN ONE SECOND.

  33. PERIOD (T) • Shortest time during which motion repeats itself. • NUMBER OF SECONDS a complete wave cycle takes to pass a fixed point • The time it takes for the swing to return to the “up” position or to complete a cycle.

  34. What is the relationship between frequency and period? Period and frequency have an inverse relationship.

  35. How do you define wavelength?

  36. Wavelength (): • The length of one complete cycle of a wave • From crest to crest (or from any point on the wave to the next identical point) • Represented by the Greek letter “Lambda” Wavelength does NOT effect speed!

  37. WAVELENGTH(shortest distance between 2 points.)

  38. Amplitude: Maximum displacement from rest or equilibrium (Half the distance between highest and lowest points)

  39. For example: • Cassie attaches a slinky to the wall and begins introducing pulses with different amplitude. Which of the two pulses (A or B) below will reach the wall first? Justify your answer.

  40. How does this relate to energy? • To produce a wave with larger amplitude, must do more work • Waves with larger amplitudes transfer more energy

  41. REVIEW • Do all waves require a medium?

  42. Answer: speed = 2 m x 500 Hz = 1000 m/s • Changing Wave Direction • Reflection: When waves bounce off a surface. • If the surface is flat, the angle at which the wave hits the surface will be the same as the angle at which it leaves the surface (angle in = angle out). • This is the law of reflection.

  43. Start for 4th

  44. 2. Refraction: Waves can bend. This happens when a wave enters a new medium and its SPEED CHANGES. The amount of bending depends on the medium it is entering.

  45. Reflection of waves • Occurs when a wave strikes a medium boundary and “bounces back” into original medium. • Completely reflected waves have the same energy and speed as original wave.

  46. What happens if a wave hits a fixed boundary?Open ended?

  47. Reflection Types • Fixed-end reflection: The wave reflects with inverted phase. • Open-end reflection: The wave reflects with the same phase Animation courtesy of Dr. Dan Russell, Kettering University

  48. Refraction of waves • Transmission of wave from one medium to another. • Refracted waves may change speed and wavelength. • Refraction is almost always accompanied by some reflection. • Refracted waves do not change frequency. Animation courtesy of Dr. Dan Russell, Kettering University

  49. Principle of Superposition • When two or more waves pass a particular point in a medium simultaneously, the resulting displacement at that point in the medium is the sum of the displacements due to each individual wave. • The wavesinterfere with each other.

  50. Types of interference. • If the waves are “in phase”, that is crests and troughs are aligned, the amplitude is increased. This is called constructive interference. • If the waves are “out of phase”, that is crests and troughs are completely misaligned, the amplitude is decreased and can even be zero. This is called destructive interference.

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