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3 Waves

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  1. Waves units

    1. 3.1

      Use the following units: degree (°), hertz (Hz), metre (m), metre/second (m/s) and second (s)

  2. (b) Properties of waves

    1. 3.2Longitudinal and transverse waves

      Explain the difference between longitudinal and transverse waves

    2. 3.3Wave definitions

      Know the definitions of amplitude, wavefront, frequency, wavelength and period of a wave

    3. 3.4Wave energy transfer

      Know that waves transfer energy and information without transferring matter

    4. 3.5Wave speed equation

      Know and use wave speed = frequency × wavelength, v = fλ.

    5. 3.6Frequency and period

      Use frequency = 1 ÷ time period, f = 1/T.

    6. 3.7Wave equations in context

      Use the above relationships in different contexts, including sound waves and electromagnetic waves

    7. 3.8Doppler effect

      Explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer and that this is known as the Doppler effect

    8. 3.9Reflection and refraction

      Explain that all waves can be reflected and refracted

  3. (c) The electromagnetic spectrum

    1. 3.10Electromagnetic spectrum

      Know that light is part of a continuous electromagnetic spectrum that includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations, and that all these waves travel at the same speed in free space

    2. 3.11EM spectrum order

      Know the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum

    3. 3.12Uses of EM radiation

      Explain some of the uses of electromagnetic radiations, including: • radio waves: broadcasting and communications • microwaves: cooking and satellite transmissions • infrared: heaters and night vision equipment • visible light: optical fibres and photography • ultraviolet: fluorescent lamps • x-rays: observing the internal structure of objects and materials, including for medical applications • gamma rays: sterilising food and medical equipment

    4. 3.13Risks of EM radiation

      Explain the harmful effects of excessive electromagnetic-wave exposure: microwave internal heating, infrared skin burns, ultraviolet surface-cell damage and blindness, and gamma-ray cancer and mutation; describe simple protective measures.

  4. (d) Light and sound

    1. 3.14Light waves

      Know that light waves are transverse waves and that they can be reflected and refracted

    2. 3.15Law of reflection

      Use the law of reflection (the angle of incidence equals the angle of reflection)

    3. 3.16Ray diagrams

      Draw ray diagrams to illustrate reflection and refraction

    4. 3.17Refraction practical

      Practical: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms

    5. 3.18Refractive index equation

      Know and use refractive index n = sin i ÷ sin r.

    6. 3.19Glass refractive index practical

      Practical: investigate the refractive index of glass, using a glass block

    7. 3.20Total internal reflection

      Describe the role of total internal reflection in transmitting information along optical fibres and in prisms

    8. 3.21Critical angle

      Explain the meaning of critical angle c

    9. 3.22Critical angle equation

      Know and use sin c = 1/n for critical angle c and refractive index n.

    10. 3.23Sound waves

      Know that sound waves are longitudinal waves that can be reflected and refracted

    11. 3.24PHuman hearing range

      Know that the frequency range for human hearing is 20–20 000 Hz

    12. 3.25PSpeed of sound practical

      Practical: investigate the speed of sound in air

    13. 3.26POscilloscope and microphone

      Understand how an oscilloscope and microphone can be used to display a sound wave

    14. 3.27PSound frequency practical

      Practical: investigate the frequency of a sound wave using an oscilloscope

    15. 3.28PPitch and frequency

      Understand how the pitch of a sound relates to the frequency of vibration of the source

    16. 3.29PLoudness and amplitude

      Understand how the loudness of a sound relates to the amplitude of vibration of the source