10 minutes maximum! Can you do it in 5?

 1. A standing wave is typically formed by 2 waves meeting. Which of these statements about the 2 waves is correct?

  • A. The waves must be travelling in the same direction, and have different wavelengths.
  • B. The waves must be travelling in opposite directions, and have different wavelengths.
  • C. The waves must be travelling in the same direction, and have the same wavelength.
  • D. The waves must be travelling in opposite directions, and have the same wavelength.
2&3. A travelling wave produces a changing wave displacement at all points, but a constant amplitude at all points. A standing wave, however, produces nodes and antinodes.  

2. What is the distance between consecutive nodes?

  • A. ¼λ
  • B. ½λ
  • C. λ
  • D. 2λ

3. An antinode is a point where...

  • A. The amplitude detected will be small, but not zero.
  • B. The amplitude detected will be zero.
  • C. The amplitude detected will be at a maximum.
  • D. The amplitude detected will rise and fall constantly.

4&5. A microphone is placed between two loudspeakers, producing identical in phase sound waves. A standing wave is formed between the speakers.

The wavelength of the sound is 20 cm.

standing wave diagram, two speakers and microphone

  

4. The microphone is moved between P and R in the diagram. Which of these statements is correct?

  • A. The amplitude detected will be constant.
  • B. The amplitude detected will gradually increase.
  • C. The amplitude detected will gradually decrease.
  • D. The amplitude detected will rise and fall several times.

5. The microphone is moved between Q and S in the diagram. Which of these statements is correct?

  • A. The amplitude detected will be constant.
  • B. The amplitude detected will gradually increase.
  • C. The amplitude detected will gradually decrease.
  • D. The amplitude detected will rise and fall several times.

6. The diagram below shows a standing wave. It is produced by a sound wave inside a pipe. The pipe has not been shown.

standing wave digram for wave in pipe

  

Which of these statements is correct?

  • A. The diagram shows the first harmonic of a pipe open at both ends.
  • B. The diagram shows the second harmonic of a pipe open at both ends.
  • C. The diagram shows the first harmonic of a pipe closed at one end.
  • D. The diagram shows the second harmonic of a pipe closed at one end.

7. A thin pipe of length 30cm is closed at one end. By blowing across the open end, different harmonics can be produced.

pipe closed at one end

 

  

What is the wavelength of the third harmonic?

  • A. 30 cm
  • B. 40 cm
  • C. 60 cm
  • D. 120 cm

8&9: The diagram shows a standing wave formed on a stretched wire.

standing wave on a wire

  

8. Which of the following correctly describes the movement of points Q and R compared to point P?

  Q R
A 900 out of phase with P 1800 out of phase with P
B In phase with P 1800 out of phase with P
C 1800 out of phase with P In phase with P
D 900 out of phase with P In phase with P

9. On the diagram above, what is this harmonic for the stretched wire and what is the length of the wire in terms of the wavelength λ?

  Harmonic length of wire
A 1st λ/2
B 1st λ
C 2nd λ/2
D 2nd λ

10. A measuring cylinder containing some water is used to make an air column closed at one end.

A sound is produced using a tuning fork. The water level in the cylinder is adjusted until the air tube resonates and a louder sound is heard.

Using this method, the first harmonic is found when the air column is 10 cm long.

resonance of air column in measuring cylinder
What is the wavelength of the sound wave produced?
  • A. 2.5 cm
  • B. 5 cm
  • C. 20 cm
  • D. 40 cm