CCEA GCSE Physics 2.1 Waves Exam Questions

About CCEA GCSE Physics 2.1 Waves

Waves is the first topic of Unit 2 in CCEA GCSE Physics (Waves, Light, Electricity, Magnetism, Electromagnetism and Space Physics). It covers how waves transfer energy without transferring matter, the difference between transverse and longitudinal waves, and the terms frequency, wavelength and amplitude. You need to use the wave equation, describe reflection and refraction using a ripple tank, and use echoes to calculate distances in ultrasound, sonar and radar. The topic finishes with the order, properties, uses and dangers of the electromagnetic spectrum. It leads into light in 2.2 and links to red shift in space physics. Examiners often set echo calculations and ask for electromagnetic spectrum order.

What you need to know

• Types of wave Waves transfer energy from one place to another. In transverse waves (light, water waves, all electromagnetic waves) vibrations are at right angles to the direction of energy transfer. In longitudinal waves (sound) vibrations are parallel to the direction of energy transfer, producing compressions and rarefactions.
• Wave terms Amplitude is the maximum displacement from the rest position. Wavelength is the distance between two neighbouring crests (or compressions). Frequency is the number of waves passing a point per second, in hertz (Hz).
• Wave equation Wave speed = frequency x wavelength, v = fλ. Speed in m/s, frequency in Hz and wavelength in m.
• Reflection and refraction In a ripple tank, plane waves reflect from a barrier with angle of incidence equal to angle of reflection. When water waves pass into shallow water they slow down, their wavelength decreases and their direction changes if they meet the boundary at an angle; frequency stays the same.
• Echoes, ultrasound, sonar and radar Ultrasound has frequencies above 20 000 Hz, beyond human hearing. Sonar uses ultrasound echoes to find the depth of the sea or locate objects; radar uses radio waves or microwaves to locate aircraft. Distance = speed x time / 2, because the wave travels there and back.
• Electromagnetic spectrum In order of increasing frequency (decreasing wavelength): radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays. All travel at 3 x 10^8 m/s in a vacuum. Higher frequency waves such as ultraviolet, X-rays and gamma rays are ionising and can damage cells and cause cancer.

Common mistakes in 2.1 Waves

• Forgetting to halve the time in echo calculations. The pulse travels to the object and back.
• Saying sound is a transverse wave. Sound is longitudinal.
• Stating that frequency changes when a wave refracts. Speed and wavelength change; frequency stays the same.
• Measuring wavelength from a crest to the next trough. Measure from crest to crest.
• Mixing up the order of the electromagnetic spectrum, especially placing ultraviolet beyond X-rays.

Try three 2.1 Waves exam-style questions