school

Science Department

Physics

SPH 4A0

SOUND TEST

PART A - Multiple Choice (15 marks)

1) Three kinds of waves are given below:

I. torsional waves

II. longitudinal waves

III. transverse waves

The sound of church bells is transmitted to your ears by

(A) I only (B) II only (C) III only (D) I and II only

2) Which of the following CANNOT transmit sound?

(A) alcohol (B) fibreglass (C) iron (D) vacuum (E) wood

3) The speed of sound depends most on

(A) the amplitude of the sound wave

(B) the intensity of the sound

(D) the transmitting medium

(E) the pitch of the sound

4) Which of the following statements is false?

(A) A sound wave transmits energy

(B) A sound wave consists of compressions and rarefactions

(D) A sound wave travels faster in a vacuum than in air

(E) A sound wave obeys the laws of reflection

5) The average speed of sound outside is

(A) largest in spring

(B) largest in summer

(D) largest in winter

(E) the same for all seasons

6) If the temperature of the air increases by 15^oC, the speed of sound in the air

(A) decreases by 0.60 m/s

(B) increases by 0.60 m/s

(D) increases by 9.0 m/s

(E) increases by 24 m/s

7) Frequencies lower than 25 Hz are called

(A) ultrasonics (B) infrasonics (C) supersonic (D) X-rays

8) A frequency of 100 Hz represents a period of

(A) 100 s (B) 10 s (C) 0.1 s (D) 0.01 s (E) 0.001 s

9) In a medium where the speed is constant, how is the wavelength related to the frequency?

(A) if ¦, λ (B) if ¦¯, λ¯ (C) if ¦, λ¯ (D) none of these

10) The following diagram represents a wave travelling down a rope. Two points that are in phase are

(A) A and C (B) B and D (C) B and E (D) A and E (E) A and F

11) As the distance from a source increases, the intensity of the sound

(A) increases (B) decreases (C) stays the same (D) is louder

12) The part responsible for equalizing the air pressure in the middle ear is the

(A) eardrum (B) stirrup (C) cochlea (D) anvil (E) eustachian tube

13) The threshold of pain occurs at an intensity level of

(A) 0 dB (B) 160 dB (C) 50 dB (D) 130 dB (E) 10 dB

14) A device that uses the principles of sound reflection to measure the depth of the ocean is a(n)

(A) echo-sounder (B) tuning fork (C) parabolic microphone (D) radar

15) The ability of waves to move around an obstacle or through a small opening is called

(A) an echo (B) refraction (C) diffraction (D) dispersion

PART B - True and False ( 10 marks)

1) Sound travels faster in air than it does in water.

2) A vibrating source is necessary for the production of sound.

3) Sound is transmitted through the air by means of transverse waves.

4) On a warm day, the speed of sound in air is greater than on a cool day.

5) The speed of sound in air increases as the temperature increases.

6) The units for period are Hertz (Hz).

7) The speed of sound at -20^oC is 344 m/s.

8) An echo can be heard by the human ear only if the time interval between the original sound and the reflected sound is less than 0.1 s.

9) At night, sound is refracted towards the surface of the earth.

10) Higher frequency sounds diffract more than lower frequency sounds.

PART A - Multiple Choice Answers Name: _________________________

1) _____ 5) _____ 9) _____ 13) _____

2) _____ 6) _____ 10) _____ 14) _____

3) _____ 7) _____ 11) _____ 15) _____

4) _____ 8) _____ 12) _____

PART B - True and False Answers

1) _____ 2) _____ 3) _____ 4) _____ 5) _____

6) _____ 7) _____ 8) _____ 9) _____ 10) _____

PART C - Short Answer (21 marks)

Marks

6 1) Define any three (3) of the following six terms.

diffraction, refraction, amplitude, wave, wavelength, rarefaction

1 2) On what does the speed of sound depend? _______________

1 3) When a wave enters a different medium, what characteristic of the wave remains unchanged? ________________

3 4) An echo is sound reflected from a distant object such as a wall or a cliff. Explain how you can determine how far away the object is by timing the echo.

8 5) Label any four (4) parts of the human ear AND explain their function.

2 6) With the aid of a graph, explain how the intensity of a sound varies with the distance from the source.

PART D - Problem Solving

1) Todd and Keith have decided to spend Saturday morning fishing for salmon. They are sitting on the edge of a bridge, 30 m apart. Waves pass below them in such a manner that when a crest is under one of them, a trough is located under the other, with two crests located between them. The cork attached to each line bobs up and down 15 times per minute and the temperature of the air is 20^oC. Determine the speed of the water waves.

2) A large lake freighter approaches a steep cliff several kilometres away and sounds a short blast of its horn. The echo is heard 20.0 seconds later. Twenty minutes later another blast produces an echo which returns in 6.0 seconds. Determine the speed of the ship in km/h, if the temperature is 18^oC.

3) A 360 Hz source emits waves having a wavelength of 24 cm. In what time will this disturbance travel a distance of 144 m?

4) A vibrating loudspeaker at one end of a horizontal column of air in a tube vibrates at 1.2 kHz. Fine cork dust is sprinkled along the bottom of the tube. The end of the tube opposite the loudspeaker is closed. The standing waves in the air in the tube cause piles of cork dust to form at the nodes. The distance form the 1st pile to the 5th is 58 cm. What is the speed of the wave in the column of air?

5) An F-14 Tomcat can fly at Mach 2.3. What is its speed in km/h at sea level, and at 15^oC?

6) A positive pulse is created in medium P. The speeds of pulses in mediums P, Q, and R are 4.5 cm/s, 2 cm/s, and 3 cm/s, respectively. Draw a diagram to show the nature and position of the reflected and transmitted pulses when the original pulse reaches the middle of medium R.

7) Using the Principle of Superposition, determine the resultant displacement of the two waves interacting as shown.