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GCSE Combined Science · key term
An imaginary line perpendicular to a boundary at the point where a ray meets it.
Used by AQA and Edexcel
Specification 6.6.2.2 · Paper 6
Revise: Electromagnetic Wave Properties and RefractionTo describe a ray's direction at a boundary, draw a normal: an imaginary line at right angles to the boundary, passing through the point where the ray meets it. The angle of incidence is between the incoming ray and the normal. The angle of refraction is between the refracted ray and the normal.
Paper 5, Paper 6
An imaginary line perpendicular to a boundary at the point where a wave meets it.
Measure angles between each ray and the normal, not between the ray and the boundary.
Use the change in wave speed to decide the bending direction; entering a material does not always mean bending towards the normal.
Measure angles from the normal, not from the boundary.
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To describe the bending, draw a normal: an imaginary line at right angles to the boundary where the ray meets it. Both the angle of incidence, before crossing, and the angle of refraction, after crossing, are measured from this line.
An imaginary line drawn at right angles to a surface at the point where a ray meets it.