Revision Notes

3.2.1 Reflection of Light

Incidence & Reflection

  • Light is part of the electromagnetic spectrum – a family of transverse waves
  • As with all wave, when light reflects:

light-reflection, IGCSE & GCSE Physics revision notes

Angle of incidence, i = angle of reflection, r


  • When an object is placed in front of a mirror, an image of that object can be seen in the mirror
  • The image:
    • Is the same size as the object
    • Is the same distance behind the mirror as the object is in front of it
    • Is directly in line with the object
Extended Only

Virtual Image & Ray Diagram

  • The formation of this image can be understood by drawing a ray diagram

Reflection ray diagram, IGCSE & GCSE Physics revision notesDiagram showing the formation of an image in a mirror by the reflection of light

  • Light from the object hits the mirror, reflecting from it (i=r)
  • To an observer, the reflected ray appears to have come from the right-hand side of the mirror
  • The reflected ray can be traced back in this directions, forming a virtual ray
  • This can be repeated for another ray travelling in a slightly different direction
  • An image of the object will appear where these two virtual rays cross
  • The type of image formed in the mirror is called a virtual image
  • A virtual image is formed by the divergence of rays from the image, and cannot be projected onto a piece of paper (because the rays don’t actually go through the image)

Exam Tip

When drawing light waves being reflected take care to get the angle about right.

If they are slightly out it won’t be a problem, but if there is an obvious difference between the angle of incidence and the angle of reflection then you will probably lose a mark.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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