Chapter 14 Waves Types Characteristics Interactions

Types of Waves Dr. B-Z

1. Define Wave  A wave is a disturbance that carries energy though matter or space.

2. The matter through which a wave travels is called a _.  Medium  Examples  Pond  Air  Earth

3. Define Mechanical Waves  Waves that require a medium are called mechanical waves  Nearly all waves are mechanical waves except for electromagnetic waves.

4.  The type of wave that consists of changing electric and magnetic fields in space is called electromagnetic waves.

5.  Energy is the ability to exert a force over a certain distance or the ability to do work.

6. What is a tsunami?  Huge ocean wave caused by an underwater earthquake  It is NOT a tidal wave.

Tsunami Flooding

Time = 0 Destructive tsunamis originate primarily in subduction zones around the Pacific Rim. Not every earthquake generates a tsunami. Model simulations combined with real-time tsunami measurements will help assess the hazard. A simulated tsunami generated by a large subduction earthquake (Mw = 8.5) in Alaska-Aleutian Subduction Zone.

Data network D eep-ocean A ssessment and R eporting of T sunamis System Surface Buoy and BPR Deployment Quality Control Web Page Simulated Tsunami and DART Reporting Modes

Computer Models allow scientists to figure out where tsunamis are most likely to strike and that is supposed to help officials find ways to put evacuation plans in place.

What went wrong on Dec. 26, 2004 when 216,000 people died?  Warning system was not in place for the Indian Ocean as it is for the Pacific Ocean  Evacuation routes were not marked

7. Why do speakers need to amplify sound?  Although each wave has the same energy, but as the waves get spread out over a larger area, the energy also gets spread out over a larger area.

8. Most waves are caused by  Vibrations of matter  Even EM waves which do not require a medium are caused by the vibrating of charged particles

9.  Both swinging pendulums and springs bobbing back and forth are examples of how vibrations transform energy.

10. What is simple harmonic motion in a spring?  When a spring is expanded or compressed, it is exerting a force that pushes the mass back almost to the original resting position. As a result, the mass will continue to bounce up and down which is an example of simple harmonic motion.

11.  A vibration that fades out as energy is transferred from one object to another is called damped harmonic motion. An example of this is when springs are attached to both a block of wood and each other. You can see a different motion than when there is just the expansion and contraction of the spring.

12. List the two ways that a wave can move.  Back and forth (horizontally)  Up and down (vertically)

 13. Waves in which the particle is perpendicular to the motion of the wave as a whole are called transverse waves  14. Wave of people in a stadium  15. Draw a picture of a Figure 6 on page 460.

16-18

#16-18  16. Waves that cause the medium to vibrate parallel to the direction of the wave motion are called longitudinal waves.  17. Examples: spring moved horizontally  18. Particle motion Wave motion

19.  Water waves are examples of surface waves.

20.  This type of wave occurs on the boundary between two different mediums.

21.  The particles in surface waves move both perpendicularly and parallel. *

Waves Pre-Assessment Characteristics of Waves

1 and 2. Draw & label a sine curve. Crests Wavelength amplitudeamplitude Trough DisplacementDisplacement

3.  The highest points on a transverse wave are called crests.

4.  The lowest points on a transverse wave are called the troughs.

5.  The greatest distance that particles are displaced from their normal resting positions because of a wave is called the amplitude.

6. Define compression  Compression is crowded coiled areas on a spring. Area of compression

7. Define rarefaction  Stretched out areas on a spring. Area of rarefaction

8.  The distance from one crest of a wave to the crest of the next wave is called the wavelength.

9.  The time required for one full wavelength of a wave to pass a certain point is called the period.

10.  The frequency of a wave is the number of full wavelengths that pass a point in a given time interval.

11. W rite the frequency-period equation.  Frequency ( f ) = 1/period or 1/T  Frequency is measured in Hertz and period is measured in seconds.

12. T he full range of light at different frequencies is called the EE M spectrum.

13. Frequency is measured in the unit of  HERTZ (Hz)  Or Cycles/second

14. W avelength is measured in the unit of LL ENGTH (meter) II t could also be in nm, cm, or mm.

15. S peed =  Wavelength ( ) / period (T)  The Greek letter lamda ( ) is the symbol for wavelength

16. Speed =  Frequency ( f ) / wavelength ( )  Or f /

17. The symbol for frequency is ff  What unit is used to measure frequency?  Hertz (Hz)

18. The symbol for wavelength is   Typically wavelength is measured in nanometers (nm)

19. Write the wave-speed equation.  V = f x  V = velocity or speed  f = ?  Frequency  = ?  wavelength

20. Sound travels better and faster in  water

21.  Sound waves travel faster in solids than in air or water. (air and water can be in either order)

22.  The speed of a wave depends on the medium.  A medium is the substance that the wave is traveling in or through.

23.  In a given medium the speed of the wave remains the same, but the frequency increases and the wavelength decreases.

24.  Electromagnetic waves (such as visible light) do NOT need a medium.

25.  The symbol c stands for the speed of light which is known to be equal to 3 x 10 8 m/s.

26.  Pitch is determined by frequency at which sound waves strike your ear drum.  The higher the frequency = higher the pitch

27.  Doppler effect refers to a body IN MOTION. When the object is coming towards you, the frequency is HIGHER than the frequency when the object is going AWAY. So when the object is moving toward you the sound has a HIGHER pitch (due to higher frequency. *

Wave Interactions Pre-Assessment

1. Define Reflection  The bouncing back of a wave when it meets a surface boundary

2. Draw a wave being reflected on a fixed boundary.  Direction of movement

3 and 4 Bending of waves as they pass an edge is called diffraction. Draw waves being diffracted around a single obstacle. Obstacle

5.  Refraction is the bending of waves when they pass from one medium to another at an angle.

6.  What type of wave interaction is shown when two or more waves combine?  Answer: Interference

7. Draw an example of constructive interference Resulting Wave Original Waves

8. Draw an example of destructive interference. Resulting Original Waves

9.  Two different sounds have two different frequencies.

10. Explain how you hear beats. Describe in terms of constructive and destructive interferences.  Alternating loud and soft sounds cause us to hear beats. The loud sound is heard because of constructive interference. The softer sounds are due to destructive interference.

11.  Standing waves can form when a wave is reflected at the boundary of a medium. In a standing wave, interference of the original wave with the reflected wave causes the medium to vibrate in a stationary pattern that resembles a loop.

12. Draw a standing wave with 5 nodes and 4 antinodes. Label them. NODES Antinodes

#16-18  16. Waves that cause the medium to vibrate parallel to the direction of the wave motion are called longitudinal waves.  17. Examples: spring moved horizontally  18. Particle motion Wave motion

19.  Water waves are examples of surface waves.

20.  This type of wave occurs on the boundary between two different mediums.

21.  The particles in surface waves move both perpendicularly and parallel. *