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Doppler Effect worksheet

Grades 11–12

Solve each problem and show your work. Round answers to 2 decimal places where needed.

  1. Problem 1.
    • Sign convention for the speeds: Positive = the direction pointing from source to observer
    • Emitted frequency (f): 450 Hz
    • Wave speed in the medium (v): 360 m/s
    • Source velocity (vₛ): 35 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  2. Problem 2.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 350 Hz
    • Wave speed in the medium (v): 340 m/s
    • Source velocity (vₛ): 26 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  3. Problem 3.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 450 Hz
    • Wave speed in the medium (v): 325 m/s
    • Source velocity (vₛ): 36 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  4. Problem 4.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 350 Hz
    • Wave speed in the medium (v): 280 m/s
    • Source velocity (vₛ): 32 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  5. Problem 5.
    • Sign convention for the speeds: Positive = the direction pointing from source to observer
    • Emitted frequency (f): 400 Hz
    • Wave speed in the medium (v): 500 m/s
    • Source velocity (vₛ): 26 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  6. Problem 6.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 600 Hz
    • Wave speed in the medium (v): 380 m/s
    • Source velocity (vₛ): 30 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  7. Problem 7.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 450 Hz
    • Wave speed in the medium (v): 380 m/s
    • Source velocity (vₛ): 28 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  8. Problem 8.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 440 Hz
    • Wave speed in the medium (v): 225 m/s
    • Source velocity (vₛ): 28 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  9. Problem 9.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 550 Hz
    • Wave speed in the medium (v): 290 m/s
    • Source velocity (vₛ): 36 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

  10. Problem 10.
    • Sign convention for the speeds: Positive = moving toward the other
    • Emitted frequency (f): 500 Hz
    • Wave speed in the medium (v): 220 m/s
    • Source velocity (vₛ): 32 m/s
    • Observer velocity (vₒ): 0 m/s

    Find: Observed frequency (f′)

Answer key: Doppler Effect worksheet

  1. 1. Observed frequency (f′): 498.46 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      450×360+0360−35=450×360325=498.461538 Hz
    2. Take away the starting tone to see how far the pitch moved

      498.461538−450=48.461538 Hz
  2. 2. Observed frequency (f′): 378.98 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      350×340+0340−26=350×340314=378.980892 Hz
    2. Take away the starting tone to see how far the pitch moved

      378.980892−350=28.980892 Hz
  3. 3. Observed frequency (f′): 506.06 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      450×325+0325−36=450×325289=506.055363 Hz
    2. Take away the starting tone to see how far the pitch moved

      506.055363−450=56.055363 Hz
  4. 4. Observed frequency (f′): 395.16 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      350×280+0280−32=350×280248=395.16129 Hz
    2. Take away the starting tone to see how far the pitch moved

      395.16129−350=45.16129 Hz
  5. 5. Observed frequency (f′): 421.94 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      400×500+0500−26=400×500474=421.940928 Hz
    2. Take away the starting tone to see how far the pitch moved

      421.940928−400=21.940928 Hz
  6. 6. Observed frequency (f′): 651.43 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      600×380+0380−30=600×380350=651.428571 Hz
    2. Take away the starting tone to see how far the pitch moved

      651.428571−600=51.428571 Hz
  7. 7. Observed frequency (f′): 485.8 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      450×380+0380−28=450×380352=485.795455 Hz
    2. Take away the starting tone to see how far the pitch moved

      485.795455−450=35.795455 Hz
  8. 8. Observed frequency (f′): 502.54 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      440×225+0225−28=440×225197=502.538071 Hz
    2. Take away the starting tone to see how far the pitch moved

      502.538071−440=62.538071 Hz
  9. 9. Observed frequency (f′): 627.95 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      550×290+0290−36=550×290254=627.952756 Hz
    2. Take away the starting tone to see how far the pitch moved

      627.952756−550=77.952756 Hz
  10. 10. Observed frequency (f′): 585.11 Hz

    1. Use the Doppler formula. Moving closer packs the waves tighter, so the pitch you hear goes up

      500×220+0220−32=500×220188=585.106383 Hz
    2. Take away the starting tone to see how far the pitch moved

      585.106383−500=85.106383 Hz