Electromagnetic waves

    AQA
    GCSE

    Electromagnetic waves are transverse oscillations of electric and magnetic fields that transfer energy from source to absorber without the requirement of a physical medium. They form a continuous spectrum ordered by wavelength and frequency, ranging from radio waves to gamma rays, all propagating at a constant velocity of 3.0 x 10^8 m/s in a vacuum. The interaction of these waves with matter—including reflection, refraction, transmission, and absorption—is determined by the relationship between the wavelength and the material structure. Candidates must understand that high-frequency waves carry sufficient energy to cause ionization in atoms, presenting significant biological hazards, while specific frequency bands are exploited for distinct applications in communication, medical imaging, and thermal energy transfer.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
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    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that all electromagnetic waves travel at the same speed in a vacuum (3 x 10^8 m/s)
    • Credit responses that link high-frequency waves (UV, X-rays, Gamma) to the ionization of atoms in living cells
    • Award 1 mark for explaining that radio waves are produced by oscillations in electrical circuits
    • For refraction diagrams (HT), award marks for showing wavefronts getting closer together when entering a denser medium (slowing down)

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that all electromagnetic waves travel at the same speed in a vacuum (3 x 10^8 m/s)
    • Credit responses that link high-frequency waves (UV, X-rays, Gamma) to the ionization of atoms in living cells
    • Award 1 mark for explaining that radio waves are produced by oscillations in electrical circuits
    • For refraction diagrams (HT), award marks for showing wavefronts getting closer together when entering a denser medium (slowing down)

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Memorize the spectrum order using a mnemonic; AQA frequently asks candidates to fill in blanks on a spectrum diagram
    • 💡When explaining uses, explicitly link the property to the application (e.g., 'X-rays are absorbed by bone but transmitted by soft tissue')
    • 💡For Required Practical 10 (Infrared), clearly distinguish between the 'emission' setup (Leslie cube) and the 'absorption' setup (heater and plates) in your method description

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing the speed of electromagnetic waves with the speed of sound, or stating speed changes with frequency in a vacuum
    • Stating that microwaves 'cook food from the inside out' rather than penetrating to heat water molecules
    • Drawing wavefronts continuous across a boundary without changing direction or spacing to represent the change in speed
    • Failing to distinguish between the effects of Infrared (heating) and Ultraviolet (ionizing/skin cancer) when discussing hazards

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

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    Practical Links

    Related required practicals

    • •{"code":"Required Practical 10","title":"Investigation of Infrared Radiation","relevance":"Investigating emission and absorption of IR by different surfaces (Leslie Cube)"}

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