# Waves and Periodic Motion What are Waves?

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Waves and Periodic Motion

What are Waves?

A WAVE is a disturbance that transfers energy from place to place. Waves are created when a source of energy causes a medium to vibrate: –A vibration is a repeated back-and-forth or up-and-down motion. –A vibration is the source of the wave The material through which a wave travels is called a MEDIUM.

Types of Waves TRANSVERSE wave – wave moved from one end to another, but medium moves perpendicular –ropes LONGITUDINAL wave – wave and medium move same direction –Springs SURFACE wave – combination of both transverse and longitudinal – occurs at surface between two mediums, like air and water –Ocean waves

Transverse Waves

Longitudinal Waves

Surface Waves KEY: Where one medium touches another (like air and water)

Waves Homework List four (4) periodic events (something that happens over and over and over List four (4) vibrations you observe around you (they can be the same 4) –Do the 4 vibrations cause a wave? –What type of wave

Properties of Waves Amplitude – maximum distance the medium moves away from its rest position (distance from rest to crest) Wavelength – distance between two troughs or two crests Frequency – number of complete waves per time (measured in hertz – wave or vibrations per second) Speed = Wavelength X Frequency

Rest Position (2.5)

Properties of Waves Speed = Wavelength X Frequency Frequency = Speed / Wavelength Wavelength = Speed / Frequency