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WAVES

WAVES. WARM UP!. What do you think of when you hear the word wave ? Write a brief description of what you think a wave is. Then, write a short paragraph describing a time you might have experienced waves. START UP ACTIVITY. TURN TO PAGE 573 COMPLETE THE ACTIVITY ON ENERGETIC WAVES

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WAVES

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  1. WAVES

  2. WARM UP! • What do you think of when you hear the word wave? Write a brief description of what you think a wave is. Then, write a short paragraph describing a time you might have experienced waves.

  3. START UP ACTIVITY • TURN TO PAGE 573 • COMPLETE THE ACTIVITY ON ENERGETIC WAVES • ON THE BACK OF YOUR WARM-UP ANSWER ANALYSIS QUESTIONS 1-3 IN COMPLETE SENTENCES • THIS WILL BE COLLECTED!

  4. REVIEW-What are the 7 forms of energy? • 1. Mechanical (potential and kinetic) • 2. Electromagnetic (light) • 3. Chemical (stored in bonds-fuel, food, batteries) • 4. Electrical (movement of electrons) • 5. Thermal (heat) • 6. Nuclear (fission and fusion) • 7. Sound

  5. WHAT IS A WAVE? • A TRANSFER OF ENERGY through matter OR empty space • A MEDIUM is any material that a wave travels through. A medium can be a solid, liquid or gas.

  6. Can anyone describe the energy transfers that are occurring here? MovingObject Wavesshow transfer of energy from propeller through water Medium=Water

  7. NATURE OF WAVES • As a wave travels, it does work on everything in its path. • The waves in a pond do work on the water when it makes the water move up and down. • The waves also do work on anything floating on the water’s surface.

  8. NATURE OF WAVES • Waves travel through a medium, but they do not carry the medium with them.

  9. Waves travel through a medium!

  10. MECHANICAL ELECTROMAGNETIC THERE ARE 2 MAJOR CATEGORIES OF WAVES

  11. MECHANICAL WAVES • Need a medium to transfer energy! CANNOT travel through empty space • OCEAN WAVES AND SOUND WAVES ARE EXAMPLES

  12. Electromagnetic Waves? • Do not need a medium, CAN travel through empty space! • Electromagnetic waves (light waves, microwaves, x-rays) can travel through empty space

  13. NATURE OF WAVES • We now know that waves can be mechanical or electromagnetic, but there are also 3 types of waves: • Three types of waves: TRANSVERSE LONGITUDINAL SURFACE/WATER

  14. TRANSVERSE WAVES • Transverse waves move perpendicularly to the direction the wave is moving • Transverse waves are made up of CRESTS and TROUGHS • electromagnetic waves are examples of transverse waves.

  15. TRANSVERSE WAVE!

  16. TRANSVERSE WAVE! • http://www.stmary.ws/highschool/physics/home/animations3/waves/wavemotion.html

  17. Time to Practice • Use your Slinky or rope to demonstrate a transverse wave: • Work with a partner • One of you move your end of the Slinky back and forth (left and right, like a snake crawling), perpendicular to its stretched length. • The other student must hold his or her end of the Slinky still • A series of transverse waves will be generated and will travel through a medium (Slinky)

  18. LONGITUDINAL WAVES • Particles move parallel to the direction of the wave • When the particles move close together it is called COMPRESSION and when they move farther apart RAREFRACTION.

  19. LONGITGUDINAL WAVE vs. TRANSVERSE WAVES!

  20. Vibrates parallel to (in the same direction of) wave travel • sound waves • http://www.stmary.ws/highschool/physics/home/animations3/waves/wavemotion.html

  21. LONGITUDINAL WAVES! • http://www.stmary.ws/highschool/physics/home/notes/waves/intro/video/Creating_a_Longitudinal_Wave-1.mov

  22. LONGITUDINAL WAVES • Sound Waves are longitudinal waves. Sound waves travel by compressions and rarefactions of air particles.

  23. TIME TO PRACTICE! • Use your Slinky to demonstrate a longitudinal wave: • Work with a partner • Stretch it out along the table • One of you grasp and draw several coils of a stretched Slinky toward yourself • Release the coils • The other student must hold his or her end of the Slinky still • A longitudinal wave pulse will be generated and travel down the length of the Slinky.

  24. SURFACE/WATER WAVES • Surface waves look like transverse waves, but the particles of the medium move in circles rather than up and down.

  25. A combination of longitudinal & transverse

  26. Pop Quiz…you may use your notes only! • Using a Venn diagram, compare and contrast mechanical and electromagnetic waves! • Draw and label the parts of a transverse and longitudinal wave. • Give one example of a type of energy that moves using a transverse wave, and one example of energy that moves using a longitudinal wave

  27. Let’s make a model! • Fold your piece of paper in half hotdog style! 2) On the top half, use some yarn to make a transverse wave. Neatly label the crest and the trough! 3) On the bottom half, make a longitudinal wave. Neatly label the compression and the rarefactions Now…put it aside…we will add more later!

  28. PROPERTIES OF WAVES

  29. THERE ARE 4 BASIC PROPERTIES OF WAVES! 1) AMPLITUDE 2) WAVELENGTH 3) FREQUENCY 4) SPEED

  30. WHAT IS AMPLITUDE? • IS THE GREATEST DISTANCE A WAVE MOVES AWAY FROM THE REST POSITION. • LARGER AMPLITUDE = MORE ENERGY!

  31. AMPLITUDE IN TRANSVERSE WAVES! • http://www.stmary.ws/highschool/physics/home/animations3/waves/Wave_Characteristics.html

  32. What about LONGITUDINAL WAVES? • MEASURE OF HOW TIGHT THE COMPRESSIONS BECOME OR HOW LOOSE THE RAREFACTIONS.

  33. WAVELENGTH • The distance between any 2 corresponding points on a wave. • For example, the distance between 2 crests in a transversal wave or 2 compressions in a longitudinal wave

  34. WAVELENGTH AND ENERGY • SHORTER WAVELENGTH = MORE ENERGY • HOW DOES SHAKING A ROPE OR A SLINKY AT DIFFERENT RATES AFFECT THE WAVELENGTH OF THE WAVE THAT MOVES THROUGH THE ROPE/SLINKY? • WRITE A HYPOTHESIS?

  35. CHANGES IN WAVLENGTH! • http://id.mind.net/~zona/mstm/physics/waves/introduction/introductionWaves.html

  36. How can you measure wavelength in longitudinal waves?

  37. FREQUENCY • The number of waves that pass a certain point in a given amount of time • Measured in HERTZ (HZ) • If 1 wave passes in 1 second the frequency is 1 Hz! • HIGHER FREQUENCY = MORE ENERGY • http://www.stmary.ws/highschool/physics/home/animations3/waves/Wave_Characteristics.html

  38. Let’s review! • http://www.classzone.com/books/ml_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html

  39. WAVE SPEED! • Speed, wavelength, and frequency are related! • Different waves travel at different speeds. • Speed = wavelength x frequency

  40. WARM UP: continued! • Draw a transverse wave with a small amplitude! • Draw a transverse wave with a large amplitude • How can I measure amplitude in a longitudinal wave? • Draw a transverse wave with a small wavelength. • Draw a transverse wave with a large wavelength. • How can I measure wavelength in a longitudinal wave? • Draw a transverse wave with a high frequency • What 2 properties of wave affect wave speed?

  41. Questions we will answer today! How do waves interact with objects? How do waves behave when they move between different mediums (media)? How do waves interact with other waves?

  42. QUESTION 1 • HOW DO WAVES INTERACT WITH OBJECTS?

  43. 1. REFLECTION • When a wave hits an object through which it cannot pass, it bounces back. This is called REFLECTION. • All waves can be reflected.

  44. Examples • When light waves are reflected off an object, that means you can see that object. For example, light waves reflecting off the moon allow you to see the moon. • When sound waves reflect it is called an echo!

  45. Reflection • When a wave reflects, the angle of incidence is equal to the angle of reflection • See for yourself.

  46. 2. Absorption and 3. Transmission • Waves that are not reflected are either absorbed OR • They are transmitted (pass through the substance) like light through a glass window or a pair of glasses

  47. 4. DIFFRACTION • Diffraction is the bending of waves around a barrier or through a opening. • The amount of diffraction of a wave depends on its wavelength and the size of the opening or barrier

  48. DIFFRACTION • If the barrier or opening is larger than the wavelength of the wave, there is only small diffraction • If the barrier is smaller, the diffraction is larger

  49. WATER WAVE DIFFRACTION

  50. DOUBLE SLIT DIFFRACTION

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