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Properties of Mechanical Waves Frequency, Period, Wavelength, Amplitude and Wave Speed (yes another formula!)

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Presentation on theme: "Properties of Mechanical Waves Frequency, Period, Wavelength, Amplitude and Wave Speed (yes another formula!)"— Presentation transcript:

1 Properties of Mechanical Waves Frequency, Period, Wavelength, Amplitude and Wave Speed (yes another formula!)

2 Period  The period of a pendulum is the time it takes to move through one cycle  This is from when the string is pulled to one side, let go and the ball moves to the opposite side and then returns to the starting place

3 Frequency  Frequency is the number of complete cycles in a given time  For a wave, the frequency is the number of wave cycles that pass a point in a given time  Frequency is measured in cycles per second or hertz (Hz)  A wave’s frequency equals the frequency of the vibrating source producing the wave

4 Equations for frequency and period  T = 1/f or f = 1/T  In the above equations: T stands for the period in time (seconds) and f stands for frequency in hertz  If given the period of an object you can calculate the frequency  Also if given the frequency of an object you can calculate the period

5 Wavelength Wavelength is the distance between a point on one wave and the same point on the next cycle of the wave For a transverse wave, wavelength is measured between crests or troughs For longitudinal waves, the wavelength is measured between compressions or rarefractions

6  V w = ƒ λ  V w = wave velocity (speed)  ƒ = frequency  λ = wavelength  Wavelength is in meters (m)  Frequency is in hertz (Hz)  Wave velocity (speed) is in meters/second (m/s)

7 Wave Speed Example One end of a rope is vibrated to produce a wave with a wavelength of 0.25 meters. The frequency of the wave is 3.0 hertz. What is the velocity of the wave? V w = ƒ λ Wavelength ( λ ) = 0.25 meters Frequency (ƒ) = 3.0Hz V w = 0.25 meters x 3.0 Hz = 0.75m/s

8 Wave Speed cont.  The speed of a wave can change if it enters a new medium or if pressure or temperature change  Most of the time, wave speed is constant  If a wave is moving at a constant speed then the wavelength is inversely proportional to frequency  waves with a lower frequency have a longer wavelength  Waves with a higher frequency have shorter wavelengths

9  The amplitude of a wave is the maximum displacement of the medium from its rest position  The more energy a wave has, the greater its amplitude


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