Physical World 1 - 11.30am

Test 3 - April 5, 2000

NAME: ________________Answers to the Pink test_____________________

(Last name, first name)

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Eighteen short answer questions. Each question is worth 5 points. (Total points = 90.)

1. A sound wave has a wavelength of 2m. Determine the period of the wave.

3. Compare the sound of a fire engine siren when it moves towards and away from you. (There may be more than one correct answer for this question.)

a) The wavelength is larger on approach compared with on departure.

d) The frequency is lower on approach compared with on departure.

e) The frequency of the siren always sounds the same.

4. a) For a standing wave what is a node?

b) For a standing wave what is an anti-node?

5. A skipper on a boat notices wave crests passing his anchor chain every 4s. He estimates the distance between wave crests to be 10m. He also correctly estimates the speed of the waves. What is this speed?

6. The sound from Source A has twice the frequency of the sound from Source B.

a) Sound A has twice the wavelength of sound B.

c) Sound A has twice the speed of sound B.

d) Sound A has half the speed of sound B.

e) None of the above.

7. X-rays, visible light, and radio waves

a) are different forms of matter.

b) all have the same wavelength.

d) all have the same period of vibration.

e) None of the above.

8. Relative to the distance of an object in front of a plane mirror, how far behind the mirror is the image?

9. A rainbow in the sky is determined by

a) the total internal reflection of light in water droplets.

b) the Doppler effect of light in water droplets.

c) the reflection of light in water droplets.

d) the diffusion of light in water droplets.

10. You hear a thunderclap 2.5s after observing a lightning strike. How far away did the lightning occur?

11. In the diagrams below are three waves which all move with the same speed.

The wave with the longest wavelength is ____________b_________________.

The wave with the lowest frequency is ____________b______________.

The wave with the largest amplitude is ____________c_____________.

(a)

(b)

(c)

12. If the wavelength of standing waves on a guitar string is 2m and the speed of the waves is 256m/s, what is the frequency of the note being played?

13. Circle the true statement.

a) The higher the pitch of a sound the higher the energy.

b) Different pitched sounds travel at different speeds.

c) The higher the pitch of a sound the longer the wavelength.

14. Explain the difference between longitudinal and transverse waves. Give an example of each.

15. In a film clip about the Tacoma Narrows bridge, the bridge collapsed because

a) the wind was very strong. The collapse had nothing to do with the frequency of the wind.

b) the frequency of the wind was much larger than the resonant frequency of the bridge.

d) the frequency of the wind was much smaller than the resonant frequency of the bridge.

16. In a demonstration a light at the bottom of a container cannot be observed by the audience when the container is empty. When the container is filled to the top with water the audience can now observe the light. This effect demonstrates the phenomenon of ______________________.

(Choose from a - e below.)

a) reflection.

b) dispersion.

c) diffraction.

e) interference.

17. In a demonstration two tuning forks of almost the same frequency are set into oscillation. The tuning forks

a) are off resonance and therefore destructively interfere.

c) resonate and therefore interfere constructively.

d) modify each others frequency due to the Doppler effect.

e) resonate and therefore sound louder.

18. Circle the correct statements. (There may be more than one correct answer for this question.)

b) Above the critical angle there is a refracted beam.

e) Total internal reflection only occurs when light is incident from a less dense to a more dense medium.

Four longer questions. Each question is worth 5 points. (Total points = 20.)

19.

The diagram above shows the shape of a sound wave at a particular instance in time.

a) Determine the amplitude of the wave.

b) Determine the wavelength of the wave.

c) Determine the frequency of the wave.

d) If this sound wave is moving towards the right and you are running towards the sound, would the wavelength of the sound that you heard be same as the answer in part b above?

If not, how would the wavelength differ?

e) If another sound wave of a slightly different frequency interfered with the wave shown in the diagram describe what you would hear. (You are standing still for this part of the question.)

20. a) Draw in the first harmonic for the closed pipe below. Be careful where you draw in the nodes and anti-nodes.

c) Repeat (a) and (b) for the third harmonic.

d) If L = 2m what is the frequency for the first harmonic?

e) If L = 2m what is the frequency for the third harmonic?

21. Bob has a tuning fork of frequency 256 Hz. He wants to make a half-open copper pipe resonate in its first harmonic.

a) Draw in the resonance pattern showing the positions of the nodes and anti-nodes inside the copper pipe.

d) What is the length of the pipe L for the first harmonic?

22. What two physics mistakes occur in a science fiction movie that shows a distant explosion in outer space, where you see and hear the explosion at the same time?