# Waves Students will learn about waves. Waves Waves transfer energy without the transfer of mass. A wave is a vibratory disturbance that is transmitted.

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Waves Students will learn about waves

Waves Waves transfer energy without the transfer of mass. A wave is a vibratory disturbance that is transmitted through a material or through space.

Mechanical Waves Mechanical waves require a material medium for transmission. The energy disturbance is propagated by the molecules of water, air, or a spring. – Transverse waves exhibit simple harmonic motion about a rest position perpendicular to the direction of motion. (EX: waves on a string) – Longitudinal waves exhibit SHM parallel to the direction of motion (EX: sound, slinky) – Surface wave exhibit motion both parallel and perpendicular to the direction (EX water waves)

Electromagnetic Waves Electromagnetic waves do NOT need a material medium for transmission. They can travel in a vacuum. (EX: light)

Period The time it takes for a wave to repeat itself Measured in seconds

Frequency Number of waves per second Frequency is the inverse of period Measured in Hertz (older measurements in 1/second or second^(-1))

Amplitude Amplitude is the maximum displacement of any particle in the medium relative to its rest position. – In a transverse wave the maximum upward displacement is the “crest” and the minimum downward displacement is the “trough” – In longitudinal waves the particles produce region of maximum compression called condensations and minimum compression called rarefactions. – Amplitude is related to the energy carried by the wave. – Amplitude in sound is Loudness; in light it is brightness.

Wavelength The distance between two successive points on a periodic wave is the wavelength. Wavelength is measured in meters. Wavelength is symbolized by the Greek letter lambda.

Speed of a wave Speed = wavelength x frequency (m/s) Wavelength = speed/frequency

Example What is the wavelength of a sound wave whose speed is 330 m/s and whose frequency if 990 Hertz? Speed = wavelength x frequency Wavelength = speed/frequency = 330 m/s/990 = 0.33 m

Speed of light All electromagnetic waves travel in space at the speed of light, c, equal to 3 x 10^8 m/s (Einstein showed that nothing can exceed the speed of light, c = 3 x 10^8 m/s)

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