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Watch Video “What do these things have in common?”

Do “The Wave”. Watch Video “What do these things have in common?”. “Waves”. What are they?. Where do they come from?. How are the made?. Good/Bad. Waves. Introduction to. Read Pg 335 ( pdf 46 ).

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Watch Video “What do these things have in common?”

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  1. Do “The Wave” Watch Video “What do these things have in common?” “Waves” What are they? Where do they come from? How are the made? Good/Bad

  2. Waves Introduction to Read Pg 335 (pdf 46)

  3. Wave: a disturbance that repeats itself regularly in space and time and transmits progressively from one particle of matter to the next, without transporting the matter. Waves are caused by vibrations and carry energy from one place to another and effect changes. These changes can be extremely useful or can cause tremendous damage.

  4. On The Side The wave is an essential unifying concept of modern physics. Matter and energy both share wave properties Take for example what is known as the electron wave partial duality theorem. Which says that an electron can exist as a wave or as a particle. In quantum physics all matter theatrically can be expressed as a wave. This is part of the premise of transportation. By having the ability to change mass into its wave function and then reassemble it in a new location.

  5. Just a Few Examples of Waves ocean waves sound waves light waves earthquakes TV and radio waves microwave ovens X-rays fiber optics lasers

  6. Wavelength: the distance between two successive wave crests, the symbol for wavelength is lambda. ( λ ) Crest : the high point of the wave. Trough: the low point of the wave. Amplitude: the distance from the midpoint or rest position of the wave to either the crest or trough of the wave.

  7. Spring Demo

  8. Classification of Waves All waves can be classified as being either a mechanical wave or an electromagnetic wave. Mechanical waves: This type of wave requires medium material. Examples, water waves, sound waves, or waves on a rope. Electromagnetic waves: This type of wave does not require medium material. Examples, light waves, radio waves, X-rays.

  9. Mechanical waves can be broken down further into two subcategories of waves. Transverse wave: Waves that cause particles over which they pass to vibrate at right angles to the direction in which the waves are moving. Example: picture a boat bobbing up and down in the water as a wave passes by. Spring Demo

  10. Longitudinal wave: Waves that cause particles over which they pass to vibrate parallel to the direction in which the waves are moving. Example: sound wave, which we will examine with greater detail later in this chapter. Spring Demo

  11. Transverse vs Longitudinal Video clip

  12. Waves Mechanical Electromagnetic Transverse Transverse Longitudinal Water Light Sound

  13. Some Cool Sites http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html http://phet.colorado.edu/index.php http://www.edumedia-sciences.com/en/a251-transverse-wave

  14. See phet site Wave pulse: A single pulse caused by a single disturbance or vibration. A constant vibration would then produce a series of continuous pulses referred to as a wave.

  15. Period: The time for one complete cycle, or vibration. The symbol for period is ( T ). Frequency: The number of cycles or vibrations that occur in one second. The units of frequency are Hertz. ( Hz ). 1 Hz is one vibration in one second. The symbol for frequency is ( f ). Period and frequency are related by the following equation.

  16. Example: A sound wave has a frequency of 262 Hz. What is the period of the wave? 3.82 x 10-3 sec

  17. Example: A mass oscillates up and down on on a spring. If the mass completes 37 cycles in a 60 second period. What is both the frequency and period of the oscillating mass. f = 0.62 Hz and T = 1.62 sec

  18. Do #’s 1- 4, Pg 341 (pdf 48)

  19. The Universal Wave Equation The universal wave equation helps us to determine wave speed, by starting with the general relationship between velocity distance and time. Now lets modify this for waves.

  20. A waves will travel a certain amount of distance, let’s say one wavelength, in a certain amount of time. The amount of time for one full wavelength to go by is what we define as the period of a wave. Therefore the standard equation for velocity can be rewritten and as follows.

  21. Now using the relationship between period and frequency we get. rearrange and simplify to get this is known as the Universal wave equation and relates velocity, wave length, and frequency of a wave.

  22. Example: A sound wave with a frequency of 262 Hz has a wavelength of 1.29 m. What is the speed of the sound wave?

  23. Example: A sound wave produced by a clock chime 515 m away is heard 1.50 sec later. a) What is the speed of sound in air?

  24. b) If the sound wave has a frequency of 436 Hz. What is its period?

  25. c) What is his wavelength?

  26. Example: A hiker shouts towards a vertical cliff 695 m away. The echoes heard 4.00 sec later. a) What is the speed of sound in air?

  27. The wave length of the sound is 0.750 m. What is the frequency?

  28. c) What is the period of the wave?

  29. Example: A radio wave, a form of an electromagnetic wave, has a frequency of 99.5 MHz. What is its wavelength?

  30. Example: A typical light wave has a wavelength of 580 nm. a) What is the wavelength of the light in meters? a) 5.8 x 10-7 m b) What is the frequency of the wave?

  31. Example: Water waves with wavelength 2.8 m, produced in a wave tank, travel at the speed of 3.80 m/s. What is the frequency of the vibrator that produced them?

  32. Do # 5 – 9, Pg 349 – 350 (pdf 49)

  33. Reflections of Waves The characteristic of a wave striking a different medium and being bounced back, either totally or partially, is termed reflection.

  34. There are two different ways in which a wave pulse can be reflected. The first is when the medium has a fixed end, or in other words the end in not allowed to move. In this case the reflected wave pulse is inverted.

  35. The second way in which a wave can be reflected is when the end of the medium is open or the end is allowed to move. In this case the reflected wave pulse is up right.

  36. See phet site If the wave strikes the medium at an angle then we have a different story. The wave will be reflected at an angle,this is know as the law of reflection.

  37. Do #’s 1-7, Pg 353 (pdf 49)

  38. Law of Reflection: The angle of incidence to the normal is equal to the angle of reflection to the normal. The normal being a ray perpendicular to the surface.

  39. Diffuse Reflection: This type of reflection is characteristic of a wave striking a rough surface and being reflected randomly (in all directions). For example, paper reflects light in all directions, therefore you can read from any angle.

  40. Sound Reflection: The reflection of sound is sometimes referred to as an echo. The percentage of sound reflected from a surface depends on the nature of the surface. For example you get a high reflection rate from a rigid, smooth surface such as, Gym walls, and low reflection from a soft, irregular surface such as, soft irregular walls in a movie theater

  41. The study of sound reflection is called acoustics.

  42. Multiple sound reflections that cause sound to be garbled are called reverberations.

  43. Interference of Waves When two or more waves occupy the same space at the same time they are said to interfere with each other. Since both waves are moving the interference will only last for a short length of time. At which point the two waves will continue on unchanged by the encounter. For that period of time when the waves are interfering with each other they can do so in two distinct ways known as constructive interference and destructive interference.

  44. Constructive interference results in a wave pulse that is bigger than either individual pulse. ( ie: they add together)

  45. Destructive interference results in a wave pulse that is smaller than either individual pulse. ( ie: they subtract from each other)

  46. See phet site

  47. http://www.kettering.edu/~drussell/Demos/superposition/superposition.htmlhttp://www.kettering.edu/~drussell/Demos/superposition/superposition.html Superposition of Waves The principle of superposition may be applied to waves whenever two (or more) waves are travelling through the same medium at the same time. The waves pass through each other without being disturbed. The net displacement of the medium at any point in space or time, is simply the sum of the individual wave displacements. This is true of both waves or pulses.

  48. Example:Use the principle of superposition to determine the resultant wave.

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