Year 9 Waves Key Terms

Rarefaction

A rarefaction is a region of a longitudinal wave where the particles of the medium are spread further apart. Its pressure and density are lower than in a compression

Refraction

Refraction is a change in a wave’s direction when it enters a different medium and its speedd changes. A wave entering straight on, changes speed but does not bend.

Reflection

Reflection occurs when a wave meets a surface or boundary and bounces back. Both longitudinal and transverse waves can reflect. The angle of incidence equals the angle of reflection, measured from the normal.

Electromagnetic waves

Electromagnetic waves transfer energy without needing a material medium. They can travel through a vacuum and are transverse waves

Mechanical waves

Mechanical waves transfer energy through a material medium as it particles vibrate around their resting positions. They cannot travel through a vacuum and may be longitudinal or transverse.

Oscillation

An oscillation is one complete back-and-forth movement around a resting position. A particle in a mechanical wave can oscillate as the wave passes.

Ripple Effect

A ripple is a small wave spreading across a surface from a disturbance. “Ripple effect“ describes the outward spread; the water does not travel all the way outward with the ripple.

Conduction

Conduction transfers thermal energh through a material from a warmer region to a cooler region by interactions between neighbouring particles. The material does not move along with the energy.

Convection

Convection transders thermal energy when warmer parts of a liquid or gas move and cooler parts move to replace them. This circulation is called a convection current.