Eduqas GCSE Physics 5 Waves in Matter Exam Questions

About Eduqas GCSE Physics 5 Waves in Matter

Waves in matter in Eduqas GCSE Physics has two parts: waves in air, fluids and solids, and waves at material interfaces and their use in exploring structures. You learn transverse and longitudinal waves, wave terms and the wave equation v = fλ. You also need to know how sound travels and is detected by the ear, what happens when waves reach a boundary, and how ultrasound and seismic P and S waves are used to explore structures that cannot be seen. Examiners often ask for wave speed calculations, echo distance questions and the evidence seismic waves give for a liquid outer core. SP5.1 investigates water waves.

What you need to know

• 5.1 Wave types Transverse waves oscillate at right angles to the direction of energy transfer, such as water waves; longitudinal waves oscillate parallel to it, with compressions and rarefactions, such as sound. Waves transfer energy, not matter.
• 5.1 Wave properties Amplitude is the maximum displacement from rest; wavelength is the distance from one point to the same point on the next wave; frequency is the number of waves per second, in hertz. T = 1/f and v = fλ. Sound needs a medium and cannot travel through a vacuum.
• 5.1 SP5.1 Investigate water waves in a ripple tank: measure the wavelength using a ruler or by freezing a stroboscope image, count waves passing a point to find frequency, and calculate wave speed.
• 5.2 Waves at boundaries At a boundary between materials a wave may be reflected, transmitted or absorbed, depending on the wavelength and the materials. Sound waves make the eardrum vibrate; human hearing is limited to about 20 Hz to 20 kHz.
• 5.2 Ultrasound Ultrasound has frequencies above 20 kHz. It is partly reflected at boundaries between tissues, and the time for echoes to return is used to build images for prenatal scans and to detect flaws in materials. Distance = speed x time / 2 for an echo.
• 5.2 Seismic waves Earthquakes produce P waves (longitudinal, travel through solids and liquids) and S waves (transverse, only travel through solids). The S wave shadow zone shows that the outer core is liquid; refraction of P waves shows changes in density.

Common mistakes in 5 Waves in Matter

• Saying waves carry matter from place to place. Waves transfer energy; the particles oscillate about fixed positions.
• Forgetting to halve the time in echo calculations. The wave travels there and back, so distance to the boundary = speed x time / 2.
• Mixing up P and S waves. P waves are longitudinal and pass through liquids; S waves are transverse and cannot pass through liquids.
• Measuring wavelength from a peak to the next trough. Wavelength is from one peak to the next peak.
• Using frequency in kHz in v = fλ without converting. Convert kHz to Hz by multiplying by 1000.

Try three 5 Waves in Matter exam-style questions