Waves

1. Waves Group #7: McKenna Wheeler, Andrea Kang, and Edward Turk

2. Equations:

3. A disturbance propagates and carries the energy. • Time period= amount of time for a wave to complete one cycle • Frequency can be found by waves/seconds. • One complete cycle includes one crest and one trough.

4. Types of waves: • Longitudinal: the energy (source)moves left and right, the disturbance moves in the same direction as the wave. These are sound waves. Compression zone to compression zone. • Transverse: the source (wave) moves up and down. An ocean wave is transverse so is light.

5. Reflection, Refraction, Diffraction, Interference. • Reflection happens when the waves bounce off a barrier and change direction. • The picture to the right shows how a light wave reflects.

6. Refraction: is when the wave undergoes a change in direction when changing mediums. • We saw this in the waves lab when the wave passed over a barrier into a shallower depth from a deep depth.

7. Diffraction: when the wave changes direction due to a gap or split in the barrier. The wave passes through or around a barrier. • The smaller the split the more diffraction occurs. • If the frequency is bigger the wavelength becomes reduced.

8. Interference: this occurs when two waves meet on the same medium. Peak to Trough. • Constructive v. Destructive interference: • Constructive: they have the same displacement. Add them together. • Destructive: have displacement in the opposite direction. Therefore, the 2 waves cancel each other out. Then both continue past each other.

9. After interference: • The meeting of the two waves DOES NOT alter the individual waves once they pass over each other. This is the principle of Superposition. Traveling v. Standing waves: Traveling waves: the wave moves or progresses across a medium. An example would be an ocean wave. The wave will pass down the rope and when it reaches the end will travel back down the rope.

10. Standing wave: the waves that seem to not move because they interfere in a way that there are points of no displacement (nodes). • Nodes= fixed points • Antinodes= the wave crest/trough that moves up and down in place.

11. Doppler Effect: • Anytime there is relative motion between the sources of a sound and the receiver of it, there is a difference between actual frequency and observed frequency. • The pitch of the ambulance siren changes as it comes closer to you.

12. Questions: • If sound travels at 330 meters per second and you hear frequency of 440hz what is the wavelength? • .63 m • .75 m • .82 m • 6 m

13. 2. What is the wavelength of the wave? • Equilibrium position • The distance from crest to trough • Distance from crest to crest • Distance from crest to the third trough

14. 3. What is the time period of the wave? • The time for one complete cycle • The number of cycles per min • the seconds divided by the wavelengths

15. 4. A bird flaps its wings 3 times per second. What is the frequency? • 6hz • 3hz • 1/3hz • 5hz

16. 5. What is a transverse wave? • Up and down motion • A sideways motion • No motion

17. 6. When a wave passes through a slit in the barrier it… • Reflects • Refracts • Diffracts • Diffusion

18. 7. Explain difference between nodes and antinodes? • Nodes have displacement, antinodes do not • Antinodes have displacement, nodes do not • Both have displacement • They resonate

19. 8. What is the period of a 440hz sound wave? • .034 • .0019 • .0022 • 14

20. 9. What change in pitch if any, occurs when a car is moving towards you? • Higher pitch • Lower pitch • No change in pitch

21. 10. If light passing through a slit causes destructive interference what happens to the light? • Light becomes brighter • Light becomes less bright • Light cancels out

22. ANSWER KEY: • B  330/440 because v=df • C • A • B  hz=cycles per second • A • C • B • C  period= 1/frequency • A • C