Physics Waves and Light Definitions

Total Internal Reflection

Complete reflection when angle of incidence exceeds critical angle into less dense medium.

Periodic Time (T)

The time a vibrating object takes to make one complete oscillation.

Frequency (f)

The number of complete oscillations made in one second.

Interference

Result when waves from two or more coherent sources overlap and combine.

Amplitude

The maximum displacement of a particle from its rest position.

Constructive Interference

When meeting waves combine to produce a greater resulting amplitude.

Wavelength (λ)

The distance between two successive crests in a wave.

Destructive Interference

When meeting waves combine to produce a smaller resulting amplitude.

Velocity of a Wave (v)

The speed at which a wave propagates through a medium or vacuum.

Coherent Sources

Sources producing waves of the same frequency and amplitude in phase.

Transverse Wave

Wave where particle displacement is at right angles to wave travel direction.

Diffraction

The spreading of waves around corners.

Polarised Wave

A wave that vibrates in a single plane after passing through a polariser.

Reflection

The bouncing of waves off an obstacle in their path.

Standing (Stationary) Wave

Wave formed when two identical waves travelling in opposite directions interfere.

Laws of Reflection

1. Angle i = angle r. 2. Incident, reflected, and normal lie in same plane.

Real Image

An image where light rays actually meet and can be projected on a screen.

Doppler Effect

Apparent change in frequency due to relative motion of source or observer.

Virtual Image

An image in which light rays only appear to meet.

Short-Sightedness

Ability to see near objects clearly but not focus on distant ones.

Refraction

The changing of direction of a wave when entering a region of different speed.

Long-Sightedness

Ability to see distant objects clearly but not focus on nearby ones.

Snell's Law (First Law of Refraction)

The ratio sin(i) / sin(r) is constant for a given pair of media.

Second Law of Refraction

Incident wave, refracted wave, and normal at incidence point lie in same plane.

Deviation

The change in direction of a light ray passing between media.

Dispersion

The breaking up of light into its constituent colours.

Critical Angle (C)

The angle of incidence for which the angle of refraction is 90°.

Primary Colours

Colours of light that cannot be made by mixing other colours.

Secondary Colours

Colours of light made by mixing two primary colours together.

Complementary Colours

A primary and secondary colour that mix to make white light.

Resonance

Occurrence where a body vibrates at its natural frequency due to another vibrating body.

Sound Intensity

power carried by sound waves per unit area