Reflection of Light (Cambridge O Level Physics)

Revision Note

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Ray Diagrams

  • Angles are measured between the wave direction (ray) and a line at 90 degrees to the boundary
    • The angle of the wave approaching the boundary is called the angle of incidence (i)
    • The angle of the wave leaving the boundary is called the angle of reflection (r)
  • The line at right angles (90°) to the boundary is known as the normal
  • When drawing a ray diagram an arrow is used to show the direction the wave is travelling
    • An incident ray has an arrow pointing towards the boundary
    • A reflected ray has an arrow pointing away from the boundary

  • The angles of incidence and reflection are usually labelled i and r respectively

Reflection

Reflection

A ray diagram for light reflecting at a boundary, showing the normal, angle of incidence and angle of reflection

The Law of Reflection

  • The law of reflection states that these angles are the same:

Angle of incidence (i) = Angle of reflection (r)

Law of Reflection

Wave Reflection, downloadable IGCSE & GCSE Physics revision notes

Reflection of a wave at a boundary, i = r

Examiner Tip

When drawing light waves being reflected take care to get the angles equal.

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 lose a mark. Use a protractor to be sure of the angles. 

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Deva

Author: Deva