Waves and Oscillation

waves transport energy along a medium without transporting matter

Types of Waves

• Longitudinal Waves

• Transverse Waves

Anatomy of a wave

• Wave crest: the highest point a wave reaches. The lowest point is called its trough.

• Wave height: the vertical distance in meters from a wave’s crest to its trough.

• Wavelength: the horizontal distance between two successive crests, often measured in meters.

Amplitude: a measurement of the energy of a wave.

• the displacement of the medium from zero or the height of a wave crest or trough from a zero point.

• In the BOSS activity it’s how far to the side the washers move.

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/waves/u10l2a.html

• Period: the time between two successive wave crests.

Oscillation: the repeating motion of a wave or a material—

one back and forth movement. Earthquakes cause seismic

waves that produce oscillations in materials with many different frequencies.

Every object has a natural rate of vibration that scientists call its natural frequency. The natural frequency of a building depends on its physical characteristics, including the design and the building materials.

Frequency: the rate at which amotion repeats, or oscillates.

• number of oscillations in an earthquake wave that occur each second.

• unit for frequency is the Hertz

• 1 Hz = 1 cycle/second.

In earthquake engineering, frequency is the rate at which the top of a building sways.

Resonance: an increase in the amplitude

In this case, the distance the top of a building moves from its rest position that occurs when the frequency of the applied oscillatory force (such as earthquake shaking) is close to the natural frequency of the system.

http://www.youtube.com/watch?v=3mclp9QmCGs

http://recipes.howstuffworks.com/food-facts/wine/question603.htm

Buildings always oscillate in an earthquake.

1985 Mexico City • ground shaking

resonated with the natural frequencies of 8-to-10-story buildings.

• severe damage to medium-height buildings that had the same frequency as the ground shaking and resonated with it.

• Higher and lower buildings were hardly damaged.

Seismic sea wave: a tsunamigenerated by an undersea earthquake.

Tsunami: a potential destructive ocean wave created by an earthquake or other large-scale disturbance of the ocean floor.