AQA GCSE Physics 4.6.1 Waves in Air, Fluids and Solids Exam Questions

About AQA GCSE Physics 4.6.1 Waves in Air, Fluids and Solids

This AQA GCSE Physics section covers mechanical waves. All students learn transverse and longitudinal waves, wave properties, v = f λ and T = 1 / f, with a required practical measuring wave speed in a ripple tank and on a string. Physics only content covers reflection, absorption and transmission (with a reflection and refraction required practical), and the Higher tier only physics content covers sound waves in solids and hearing, and waves for detection and exploration including ultrasound, seismic waves and echo sounding. It is examined on Paper 2. Examiners test wave calculations, the difference between wave types and practical methods.

What you need to know

• Transverse and longitudinal In transverse waves the oscillations are perpendicular to the direction of energy transfer, for example ripples on water. In longitudinal waves the oscillations are parallel to the direction of energy transfer, showing compressions and rarefactions, for example sound in air. It is the wave, not the water or air, that travels.
• Wave properties Amplitude is the maximum displacement of a point on a wave from its undisturbed position. Wavelength is the distance from a point on one wave to the equivalent point on the adjacent wave. Frequency is the number of waves passing a point each second (Hz).
• Wave equations Wave speed = frequency x wavelength: v = f λ (memorise). Period T = 1 / f (on the equation sheet).
• Required practical Measure the frequency, wavelength and speed of waves in a ripple tank (using a strobe or photograph against a ruler) and waves on a stretched string (using a vibration generator), then use v = f λ.
• Reflection (physics only) Waves can be reflected, absorbed or transmitted at a boundary. A required practical investigates the reflection of light by different surfaces and the refraction of light by different substances, using ray boxes and protractors.
• Sound waves (physics only, Higher tier only) Sound waves travelling through a solid cause vibrations in the solid. In the ear, sound waves make the eardrum vibrate. The range of normal human hearing is 20 Hz to 20 kHz, limited by how well conversion to vibration works at different frequencies.
• Detection and exploration (physics only, Higher tier only) Ultrasound (above 20 kHz) is partially reflected at boundaries, used for medical and industrial imaging. Seismic P-waves are longitudinal and travel through solids and liquids; S-waves are transverse and cannot travel through liquids, giving evidence for the Earth's liquid outer core. Echo sounding uses high frequency sound to find water depth.

Common mistakes in 4.6.1 Waves in Air, Fluids and Solids

• Saying the water particles travel along with a water wave. The wave transfers energy; the particles only oscillate.
• Measuring amplitude from trough to peak. Amplitude is from the undisturbed position to a peak (half of peak to trough).
• Forgetting to convert kHz to Hz or cm to m in v = f λ.
• Mixing up P and S waves. P-waves are longitudinal and travel through liquids; S-waves are transverse and cannot.
• Using the total echo time for distance. In echo questions halve the total distance because the wave travels there and back.

Try three 4.6.1 Waves in Air, Fluids and Solids exam-style questions