Waves

1. Waves By: S

2. Define mechanical waves and relate the waves to energy. Unit 5 Mechanical waves are disturbances in matter which need a medium to travel through. These waves also carry energy from place to place. For example, if you are laying on a boogie board in the ocean and a wave (which has the energy) comes along, both you and the boogie board will go up. When you are at the top of the wave you have potential energy, but when you start to move the potential energy gets transferred into kinetic energy.

3. Describe transverse, longitudinal, and surface waves. Discuss how they are produced. Unit 5

4. Identify examples of transverse and longitudinal waves. Unit 5

5. Analyze the motion of a medium as each kind of mechanical wave passes through it. Unit 5

6. Define frequency, period, wavelength, and wave speed. Describe these properties for different kinds of waves. Unit 5-2 • Frequency – The number of cycles completed in a given amount of time (usually one second). • period – The time needed for one complete cycle that returns to its starting point. • wavelength – The distance between two points, a point on one wave and the same point on the cycle of the next wave. • wave speed – distance/time Describing These Properties For Waves To find the wave speed, you have to find the distance of the wave and divide it by the time it takes for the wave to reach that distance. The top bars on this wave represent the crest and the bottom bars represent the trough. So from one crest or trough bar to the other is the period because it is a complete cycle that returns to its starting point. From one point on a wave to the to that same point on the next cycle of the wave is the wavelength. Example A would have a higher frequency than example B. This is because A has more cycles per one second than B does, which means that the waves are moving faster in example A.

7. Describe how to measure amplitude and relate amplitude to the energy of the wave Unit 5-2 To measure amplitude you have to find the height of a wave from its resting position. The greater amount of energy that the wave has, the greater that the wave’s amplitude will be.

8. Describe how reflection, refraction, diffraction, and interference affect waves. Unit 5-3

9. State a rule that explains refraction of a wave as it passes from one medium to another. Unit 5-3 A rule that explains refraction of a wave as it passes from one medium to another is that when a wave is going into a new medium at an angle, refraction takes place because one side of the wave moves more slowly than the other side.

10. Identify factors that affect the amount of refraction, diffraction, or interference. Unit 5-3 All • the type of medium that the wave is traveling through • the type of wave • the angle that the wave moves from one medium to another Refraction Only • how much the wave bends • the speed of the waves Diffraction Only • the size of the opening or obstacle • the size of the wavelength Interference Only • how much the waves overlap and combine together

11. Distinguish between constructive and destructive interference and explain how standing waves form. Unit 5-3 The difference between constructive and destructive interference is that constructive interference is when two waves combine to produce a wave with a greater amplitude and destructive interference is when two waves combine and produce a wave with smaller displacement. • constructive interference – When two waves combine, the crests of those waves will combine to produce a higher crest and the two troughs will combine to produce a lower trough. • destructive interference – When two waves combine , the crest of one wave will meet the trough of the other wave and result to have a crest lower than the crest of both of the waves (one or two). At certain frequencies, as a result of interference, two waves traveling in opposite directions can produce a standing wave.

12. Describe the properties of sound waves and explain how sound is produced and reproduced. Unit 5-4 Sound Wave Properties • speed • frequency • pitch • intensity • loudness Sound is produced when a medium is disturbed and the molecules in the medium are set into motion. To reproduce sound, you convert the electronic signals into sound waves.

13. Describe how sound waves behave in ultrasound and music Unit 5-4 In music, by changing the frequency of standing waves, the pitch that comes out will vary. So in a wind instrument the notes can either be opened or closed and depending on the length of the column of air, standing waves (sound waves) are produced. In string instruments, you can either make the strings longer or shorter using your fingers to get standing waves (sound waves). An ultrasound is sound at frequencies higher than almost every one hears. In sonar (which ultrasound is used in), waves are sent out and the distance to that object is calculated by using the speed of sound in water. When the sound waves reach an object, they bounce off and send back an echo that says where something is located.

14. Explain how relative motion determines the frequency of sound an observer hears. Unit 5-4 Relative motion determines the frequency of sound an observer hears because for instance in the Doppler Effect, as any source of sound approaches, the observer would hear a higher frequency. When the source of sound moves away, the observer would hear a lower frequency.

15. Analyze the functions of the main regions of the human ear. Unit 5-4 • outer ear – gathers while focusing sounds to the middle ear • middle ear – receives and amplifies vibrations • inner ear – senses vibrations while using nerve endings and sends signals to the brain