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    Physics Doppler Effect 1

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    Physics Doppler Effect 1

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    Download as pptx, pdf, or txt
    9 views13 pages

    Physics Doppler Effect 1

    Uploaded by

    Rose Marimira

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    You are on page 1of 13

    Unit 7.

    The Doppler Effect


    By Naomi Machipisa, Amanda Chinwadzimba, Bridgette Chitauro
    Match the concepts
    The number of oscillations or cycles of a wave that occur per unit of time.
    Wavelength It is usually measured in hertz (Hz) and is denoted by the symbol f

    Pitch is the highness or lowness of a sound. When objects vibrate they


    produce sound waves. If the sound wave is long it makes a low pitched
    Frequency sound and if the sound wave is short it makes a high pitched sound. Pitch
    is related to frequency.

    The distance between two consecutive points in a wave that are in phase,
    Sound Pitch such as the distance between two successive peaks or troughs. It is often
    denoted by the symbol λ
    Doppler Shift of Sound

    Example Explanation

    The whistle of a train or the siren This frequency change due to


    of an ambulance appears to the relative motion between a
    decrease in frequency (sounds source of sound or light and an
    lower in pitch) as it moves observer is known as
    further away from you. the doppler effect (or doppler
    shift)
    Doppler Shift of Sound

    When the observer and the source


    of sound are both stationary, the
    waves are at the same frequency for
    both the observer
    and the source.
    Doppler Shift of Sound

    When the source starts to


    move towards the observer, the
    wavelength of the waves
    is shortened.
    The sound therefore appears at
    a higher frequency to the observer.
    In summary...
    1. The frequency is increased when the source is
    moving towards the observer. Hence a higher sound
    pitch is heard.

    2. The frequency is decreased when the source is


    moving away from the observer. Hence a lower sound
    pitch is heard.
    Calculating Doppler Shift
    When a source of sound waves moves relative to a stationary observer, the
    observed frequency can be calculated using the equation below:

    The wave velocity for sound waves is 340 ms-1.


    The ± depends on whether the source is moving towards or away from the observer.
    If the source is moving towards, the denominator is v - vs
    If the source is moving away, the denominator is v + vs
    Example 1
    A police car siren emits a sound wave with a frequency of 450 Hz. The car is
    travelling away from an observer at speed of 45 m s-1. The speed of sound is
    340 m s-1.

    Which of the following is the frequency the observer hears?

    A. 519 Hz B. 483 Hz C. 397 Hz D. 358 Hz


    Answer
    Example 2
    Now you try!
    Answer
    Thank You!
    Any questions?

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