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    Doppler

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    This document describes an activity on the Doppler effect involving light and sound waves. It explains how the Doppler effect causes changes in frequency and wavelength for waves emitted by an object moving toward or away from an observer. When applied to light waves, the Doppler effect results in blueshifts or redshifts of the observed spectrum depending on whether the source is moving toward or away from the observer. The activity involves interactive simulations demonstrating these effects for sound waves and spectral lines from stars. It also discusses how astronomers use the Doppler effect caused by orbiting exoplanets to detect their presence.

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    Doppler

    Uploaded by

    api-255334265
    583 views9 pages
    This document describes an activity on the Doppler effect involving light and sound waves. It explains how the Doppler effect causes changes in frequency and wavelength for waves emitted by an object moving toward or away from an observer. When applied to light waves, the Doppler effect results in blueshifts or redshifts of the observed spectrum depending on whether the source is moving toward or away from the observer. The activity involves interactive simulations demonstrating these effects for sound waves and spectral lines from stars. It also discusses how astronomers use the Doppler effect caused by orbiting exoplanets to detect their presence.

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    This document describes an activity on the Doppler effect involving light and sound waves. It explains how the Doppler effect causes changes in frequency and wavelength for waves emitted by an object moving toward or away from an observer. When applied to light waves, the Doppler effect results in blueshifts or redshifts of the observed spectrum depending on whether the source is moving toward or away from the observer. The activity involves interactive simulations demonstrating these effects for sound waves and spectral lines from stars. It also discusses how astronomers use the Doppler effect caused by orbiting exoplanets to detect their presence.

    Copyright:

    © All Rights Reserved
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
    583 views9 pages

    Doppler

    Uploaded by

    api-255334265
    This document describes an activity on the Doppler effect involving light and sound waves. It explains how the Doppler effect causes changes in frequency and wavelength for waves emitted by an object moving toward or away from an observer. When applied to light waves, the Doppler effect results in blueshifts or redshifts of the observed spectrum depending on whether the source is moving toward or away from the observer. The activity involves interactive simulations demonstrating these effects for sound waves and spectral lines from stars. It also discusses how astronomers use the Doppler effect caused by orbiting exoplanets to detect their presence.

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    Physical Science Workshop: Astronomy Applications of Light & Color 1

    Activity: Doppler Effect


    Background:
    The Doppler effect causes a train whistle, car, or airplane to sound higher when it is
    moving towards you, and lower when it is moving away from you.

    From: http://www.physics.purdue.edu/astr263l/inlabs/doppler.html

    For sound: high pitch = high frequency = short wavelength


    Light is also a wave, and affected by the Doppler effect
    o longer wavelengths (lower frequencies) of light appear redder
    o The spectrum of a star moving towards you will appear blueshifted (shorter
    wavelengths / higher frequencies)
    o The spectrum of a star moving away from you will appear redshifted (longer
    wavelengths / lower frequencies)

    From: http://www.astrosociety.org/education/publications/tnl/55/astrocappella3.html

    Lab Materials:
    computer with internet access
    S. Sallmen Activity: Doppler Effect
    Physical Science Workshop: Astronomy Applications of Light & Color 2

    Activity:
    Doppler Basics:

    Go to: http://www.fearofphysics.com/Sound/dopwhy2.html

    1. Watch the waves reaching your ear if:


    the source moves towards your ear at 100 meters / second
    the source moves away from your ear at 100 meters / second
    a. In which case is the frequency of sound higher?

    b. In which case is the wavelength of the sound waves longest?

    c. If these were light waves, in which case would the light reaching your eye
    be redder?

    d. If these were light waves, in which case would the light reaching your eye
    be bluer?

    2. Watch the waves reaching your ear if:


    the source moves away from your ear at 100 meters / second
    the source moves away from your ear at 200 meters / second
    a. In which case is the frequency of sound higher?

    b. In which case is the wavelength of the sound waves longest?

    Doppler Shifting of Spectral Lines:


    Go to:
    http://www.classzone.com/books/earth_science/terc/content/visualizations/es2802/es2802page01
    .cfm?chapter_no=visualization
    3. Adjust the motion of the star (both towards and away) and its speed relative to the Earth.
    a. Describe what happens to the spectrum of the star if it is moving towards Earth.
    What if it is moving away from Earth?

    b. Describe what happens to the shift in the spectrum of the star if the star
    moves more quickly.
    S. Sallmen Activity: Doppler Effect
    Physical Science Workshop: Astronomy Applications of Light & Color 3
    4. Go to: http://www.pbs.org/wgbh/nova/universe/moving_nf_04.html
    a. Order the spectra, starting with the one that is moving the fastest toward us
    and ending with the one that is moving the fastest away from us. What
    sequence do you come up with?

    b. Scroll to the bottom of the page to make sure you got it right.

    5. The following diagram is from: http://woodahl.physics.iupui.edu/05-22_anno.jpg

    Blue Red
    Wavelength
    a. Which objects are moving towards Earth? _____________
    b. Which object is moving towards Earth fastest? _____________
    c. Which objects are moving away from Earth? _____________
    d. Which object is moving away from Earth fastest? _____________
    S. Sallmen Activity: Doppler Effect
    Physical Science Workshop: Astronomy Applications of Light & Color 4

    Astronomical Applications:
    Go to: http://www.astronomy.ohio-state.edu/~pogge/Ast162/Movies/specbin.html
    Watch the movie:
    The top panel shows two stars (Blue = A; red = B) orbiting one another. The
    green dot represents the Earth. This diagram is NOT TO SCALE.
    The bottom panel shows the combined absorption-line spectrum of the stars (with
    the lines from each star labeled A and B). A thin "stationary" absorption line
    appearing between the two lines shows the un-shifted location of each line.

    6. From your examination of the movie and what youve learned so far:
    a. Which star is moving faster in its orbit: A or B?

    b. Which stars absorption lines show the largest Doppler shifts: A or B?


    Explain why.

    c. How is star B moving relative to Earth when its lines are shifted the most to the
    blue?

    d. How is star B moving relative to Earth when its lines are shifted the most to the
    red?

    Go to: http://www.howstuffworks.com/planet-hunting2.htm
    Read the material and watch the animation.

    7. How do we use the Doppler effect to help us detect the presence of planets around other
    stars?
    S. Sallmen Activity: Doppler Effect

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