Waves

Waves covers transverse and longitudinal waves, the wave equation, reflection and refraction, sound, the electromagnetic spectrum and its uses and dangers, and for Triple students lenses, black body radiation and ultrasound.

Distinguish the two wave types first — in a transverse wave the oscillations are perpendicular to the direction of energy transfer, in a longitudinal wave they are parallel — since this distinction runs through the whole unit. The wave equation appears constantly and rewards careful unit handling, particularly hertz and kilohertz. The electromagnetic spectrum must be known in order, with a use and a danger for each region. Ray diagrams need a ruler and correctly labelled normals. A frequent error is describing waves as transferring matter rather than energy, which mark schemes penalise directly.