Interference and standing waves

Answer Key - Grade 11 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Waves travel at 240 m/s on a string 0.8 m long. What frequency makes a standing wave with 3 loops, Bo?

   450 Hz
2. 2.

   Waves travel at 90 m/s on a string 0.5 m long. What frequency makes a standing wave with 2 loops, Esme?

   180 Hz

3. Read this first

   Standing waves on one string (example data)

   Loops	Frequency (Hz)
   1	100
   2	200
   3	300
   4	?

4. 3.

   Using the table, the string is 0.5 m long. How fast do waves travel on it, Kira?

   • 100 m/s
   • 50 m/s
   • 200 m/s
5. 4.

   Using the table, why can't this string make a standing wave at 250 Hz, Luz?

   • Standing waves need odd numbers of loops
   • It isn't a whole-number multiple of 100 Hz
   • 250 Hz is too high for any string
6. 5.

   Milo says destructive interference destroys energy. Agree or disagree?

   • Agree: the quiet spots soak it up for good
   • Agree: cancelled waves lose their energy
   • Disagree: the energy moves to the loud spots
7. 6.

   Noah says two pulses that cancel while overlapping are gone for good. Agree or disagree?

   • Agree: they join into one flat rope
   • Agree: cancelling uses them up
   • Disagree: each carries on after they pass
8. 7.

   Pia says the nodes on a standing wave are points where two waves always cancel. Agree or disagree?

   • Agree: the two waves meet out of step there
   • Disagree: nodes move along the string
   • Disagree: nodes are where the string moves most
9. 8.

   A string's lowest note is 200 Hz. What is it if the string is held at half its length, Ren?

   • 100 Hz
   • 200 Hz
   • 400 Hz
10. 9.

    Tightening a string makes waves travel faster on it. What happens to its lowest note, Tala?

    • It stays the same
    • It rises
    • It falls
11. 10.

    Waves travel at 150 m/s on a 0.75 m string. What is its lowest standing-wave frequency, Zee?

    • 200 Hz
    • 100 Hz
    • 112.5 Hz