1. 1
   A geophysical survey company sends seismic waves down into the ground from a vibrating truck-mounted source to search for oil deposits, by detecting waves reflected back to the surface by different rock layers.

   (a)

   Which type of wave has oscillations that are perpendicular to the direction of energy transfer?

   [1 mark]

   • Astatic wave
   • Blongitudinal wave
   • Ctransverse wave
   • Dstanding wave only

   (b)

   Which of the following correctly describes a longitudinal wave?

   [1 mark]

   • Aoscillations perpendicular to the direction of energy transfer, showing crests and troughs
   • Ba wave that cannot be reflected
   • Coscillations that transfer matter along with energy
   • Doscillations parallel to the direction of energy transfer, showing compressions and rarefactions

   (c)

   A seismic wave has a frequency of 20 Hz and a wavelength of 250 m as it travels through a particular rock layer. Calculate the wave's speed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A musician plucks a guitar string, producing a sound wave that travels through the air to a listener, who notices the sound is louder when the string is plucked harder and higher-pitched when a shorter string is used.

   (a)

   What feature of a sound wave determines its loudness?

   [1 mark]

   • Afrequency
   • Bwavelength
   • Camplitude
   • Dwave speed

   (b)

   What feature of a sound wave determines its pitch?

   [1 mark]

   • Aamplitude
   • Bdirection of travel
   • Cperiod only
   • Dfrequency

   (c)

   The sound wave produced by the guitar string has a frequency of 440 Hz. Calculate its period.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Ocean scientists use echo sounding, sending sound waves down from a research ship and timing how long they take to reflect off the seabed and return, to map the depth of the ocean floor.

   (a)

   Explain how echo sounding can be used to determine the depth of the seabed beneath the ship, referring to the reflection of sound waves.

   [3 marks]

   (b)

   A pulse of sound takes 0.08 s to travel from the ship to the seabed and back again. The speed of sound in seawater is 1500 m/s. Calculate the depth of the seabed beneath the ship, explaining your method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Hospital sonographers use ultrasound scanning to produce images of internal organs and unborn babies, sending high-frequency sound waves into the body and detecting the waves reflected back from boundaries between different tissues.

   (a)

   Explain how ultrasound imaging uses the properties of waves (frequency, reflection, and wave speed) to build up an image of structures inside a patient's body, including why waves are partially reflected at a boundary between two different tissues.

   [6 marks]

   (b)

   Evaluate why ultrasound (rather than higher-energy waves such as X-rays) is generally preferred for repeated scanning of unborn babies during pregnancy, referring to the properties and safety of different parts of the electromagnetic spectrum compared with sound waves.

   [6 marks]

   Total for question 4: 12 marks

End of questions