Visible light (Physics only)

    AQA
    GCSE

    Visible light represents the specific band of the electromagnetic spectrum detectable by the human eye, interacting with matter through reflection, refraction, transmission, and absorption. Candidates must analyze how differential absorption and reflection of wavelengths determine the perceived colour of opaque objects, and how filters function by transmitting specific wavelengths while absorbing others. The topic necessitates the construction of precise ray diagrams to model image formation by convex and concave lenses, distinguishing between real and virtual images. Furthermore, the distinction between specular and diffuse reflection must be explained in terms of surface topography and parallel ray behaviour.

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    Objectives
    3
    Exam Tips
    3
    Pitfalls
    4
    Key Terms
    4
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that each colour within the visible light spectrum has its own narrow band of wavelength and frequency
    • Credit responses that explain specular reflection occurs on smooth surfaces where parallel incident rays are reflected parallel
    • Award marks for explaining that a colour filter works by absorbing certain wavelengths and transmitting others
    • Candidates must link the colour of an opaque object to the specific wavelengths of light it reflects; if all wavelengths are reflected, it appears white

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that each colour within the visible light spectrum has its own narrow band of wavelength and frequency
    • Credit responses that explain specular reflection occurs on smooth surfaces where parallel incident rays are reflected parallel
    • Award marks for explaining that a colour filter works by absorbing certain wavelengths and transmitting others
    • Candidates must link the colour of an opaque object to the specific wavelengths of light it reflects; if all wavelengths are reflected, it appears white

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When explaining diffuse reflection, explicitly mention that scattering is caused by the roughness of the surface, not by the light itself
    • 💡For questions on filters, trace the path of the light: identify incident wavelengths, state which are absorbed, and conclude which are transmitted
    • 💡Memorize the order of the visible spectrum (ROYGBIV) as wavelength decreases and frequency increases; this is often required for AO1 marks

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Stating that a red filter 'turns' white light red or adds red colour, rather than absorbing all non-red wavelengths
    • Believing diffuse reflection means the law of reflection (i=r) does not apply; it applies to each individual ray, but surface normals vary due to roughness
    • Confusing the appearance of a coloured object under coloured light (e.g., thinking a red object looks red under blue light, instead of black)

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

    State
    Explain
    Describe
    Compare
    Draw

    Practical Links

    Related required practicals

    • •{"code":"Required Practical 9","title":"Reflection and Refraction","relevance":"Foundational skills for observing light behavior which applies to visible light theory"}

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