Sound & UltrasoundOxford AQA IGCSE Physics: Subtopic test

1. 1
   A violinist plays two notes in a concert hall: one is a high-pitched note played softly, and the other is a low-pitched note played loudly.

   (a)

   What determines whether a note sounds high-pitched or low-pitched?

   [1 mark]

   • AThe amplitude of the sound wave
   • BThe frequency of the sound wave
   • CThe speed of the sound wave
   • DThe medium the sound wave travels through only

   (b)

   What determines whether the low-pitched note sounds loud or quiet to the audience?

   [1 mark]

   • AThe frequency of the sound wave
   • BThe wavelength of the sound wave only
   • CThe amplitude of the sound wave
   • DThe direction the sound wave travels in

   (c)

   Describe, in terms of the movement of air particles, how the sound wave produced by the violin string travels through the air to reach the audience's ears.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hiker stands at the bottom of a deep canyon and shouts loudly. She hears an echo of her own voice 1.2 seconds after she shouts. The speed of sound in air is 340 m/s.

   (a)

   What causes the hiker to hear an echo of her shout?

   [1 mark]

   • AReflection of sound off the canyon walls
   • BDiffraction of sound around the canyon walls
   • CRefraction of sound as it enters the rock of the canyon walls
   • DAbsorption of sound by the canyon walls

   (b)

   Later, from around a bend in the canyon where she cannot see another hiker directly, she can still clearly hear him talking. Which wave property best explains why sound can be heard around a corner like this?

   [1 mark]

   • AReflection of sound waves
   • BPolarisation of sound waves
   • CRefraction of sound waves
   • DDiffraction of sound waves

   (c)

   Calculate the distance from the hiker to the canyon wall that reflected her shout back to her.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   During a routine pregnancy check, a sonographer uses an ultrasound scanner to view the developing foetus. The scanner sends pulses of ultrasound into the mother's body and detects the reflected pulses that bounce back from boundaries between different tissues.

   (a)

   Define ultrasound, and explain why ultrasound rather than audible sound is used for this type of medical scanning.

   [3 marks]

   (b)

   An ultrasound pulse sent into the mother's body is detected back at the scanner 0.00013 s after being sent, having reflected off a boundary between two tissues. The speed of ultrasound in the tissue is 1500 m/s. Calculate the distance from the scanner to the tissue boundary, and give one advantage of using ultrasound scanning rather than X-rays to examine a developing foetus.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Decades ago, naval crews used sonar, an early application of ultrasound, to detect submarines and map the seabed by timing echoes reflected from underwater objects. Today, doctors use a similar principle of focused ultrasound in a medical treatment to break up kidney stones inside a patient's body without surgery.

   (a)

   Explain how ultrasound could be used by a ship's sonar system to determine the depth of the seabed below it, including the equation used and the measurements that would need to be taken.

   [6 marks]

   (b)

   Explain how focused ultrasound waves can be used to treat a patient with kidney stones without the need for surgery, and discuss why this method might be preferred over a surgical operation.

   [6 marks]

   Total for question 4: 12 marks

End of questions