SoundIB MYP Physics: Subtopic test

1. 1
   In a science-fiction film, a spacecraft explodes in the vacuum of space and the audience hears a loud bang. A physics teacher says this could not happen in real life, although a crew member inside the spacecraft could hear a tapping sound travelling through the metal hull.

   (a)

   Which statement correctly describes a sound wave travelling through air?

   [1 mark]

   • AA transverse wave, with the air particles vibrating at right angles to the direction of travel
   • BA longitudinal wave, with the air particles vibrating parallel to the direction of travel
   • CAn electromagnetic wave that carries energy through empty space
   • DA wave in which air particles travel from the source to the listener

   (b)

   How does the speed of sound in the steel hull compare with its speed in air?

   [1 mark]

   • AMuch faster in steel than in air
   • BSlightly slower in steel than in air
   • CThe same in steel as in air
   • DSound cannot travel through steel

   (c)

   Explain why the bang could not be heard in space.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student records two notes on a guitar. Note X has a frequency of 220 Hz and is plucked firmly. Note Y has a frequency of 440 Hz and is plucked gently. She then blows a dog whistle that makes sound of frequency 30 kHz. Her dog reacts to the whistle straight away but she hears nothing.

   (a)

   Which statement about the two guitar notes is correct?

   [1 mark]

   • ANote X has the higher pitch because it was plucked more firmly
   • BBoth notes have the same pitch because they come from the same guitar
   • CNote Y has the higher pitch because its amplitude is smaller
   • DNote Y has the higher pitch because its frequency is higher

   (b)

   Which statement about the loudness of the two notes is correct?

   [1 mark]

   • ANote Y is louder because it has the higher frequency
   • BNote Y is louder because it was plucked gently
   • CNote X is louder because its vibrations have the larger amplitude
   • DThe notes are equally loud because they are played on the same guitar

   (c)

   Explain why the dog can hear the whistle but the student cannot.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Two students measure the speed of sound in air. Hannah stands 85 m from a large, flat wall and claps her hands once. Raj, standing next to her, starts a stopwatch at the clap and stops it when he hears the echo. He repeats this five times and records the times 0.50 s, 0.54 s, 0.48 s, 0.52 s and 0.51 s.

   (a)

   Calculate the mean time and use it to calculate the speed of sound in air.

   [3 marks]

   (b)

   Evaluate the method. Identify the main source of error, suggest one improvement and comment on the reliability of the results.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital in Singapore offers both hearing tests and ultrasound scans. Audiologists test the hearing of construction workers who use loud machinery all day. In the scanning department, sonographers scan unborn babies. A probe on the mother's abdomen sends pulses of ultrasound into the body and detects the echoes that return from the boundaries between different tissues. A computer uses the echoes to build up an image.

   (a)

   Describe how sound travels through the ear to the brain, and explain how years of working with loud machinery can damage a worker's hearing.

   [6 marks]

   (b)

   Discuss and evaluate the use of ultrasound scans on unborn babies, and decide whether every pregnant woman should be offered one.

   [6 marks]

   Total for question 4: 12 marks

End of questions