Reflection (HT Only) (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Reflection

• Reflection occurs when:

A wave hits a boundary between two media and does not pass through, but instead stays in the original medium

The Law of Reflection

• The angle of incidence = the angle between the incoming ray and the normal (a line perpendicular to the boundary)

• The angle of reflection = the angle between the reflected ray and the normal

• The law of reflection states:

Angle of incidence = Angle of reflection

Reflection of a wave at a boundary

• Echos are examples of sound waves being reflected off a surface

• Flat surfaces are the most reflective

  • The smoother the surface, the stronger the reflected wave is

• Rough surfaces are the least reflective

  • This is because the light scatters in all directions

• Opaque surfaces will reflect light which is not absorbed by the material

  • The electrons will absorb the light energy, then reemit it as a reflected wave

Reflection 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 law of reflection states that these angles are the same:

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

Reflection of a wave at a boundary

• 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