Progressive Waves

Seite 1

A wave is the oscillation of particles or fields

A progressive wave carries energy from one place to another without transferring any material. A wave is caused by something forcing particles or fields to oscillate at a source. These oscillations pass through the medium or field as the wave travels, carrying energy with it.

There are numerous ways to detect when waves carry energy such as

Electromagnetic waves heat up objects

X-rays and gamma rays knock electrons out of their orbits, causing ionisation

Loud sounds cause large oscillations of air particles which can make objects vibrate

As energy is transferred by waves, the source of the wave loses

Key Definitions of a Wave

Cycle - one complete vibration of the wave

Displacement, x, metres - how far a point on the wave as moved from its undisturbed poition

Amplitude, A, metres - maximum magnitude of displacement

Wavelength, λ, metres - the length of one whole wave cycle, from crest to crest (or trough to through)

Period, T, seconds - the time taken for a whole cycle to complete, or to pass a given point

Phase - a measurement of the position of a certain point along the wave

Phase difference - the amount one wave remains behind

Phase and phase difference are measured in angles (often radians) or as fractions of a cycle

Waves Can Be Reflected and Refracted

Reflection - the wave is reflected when it comes into contact with a boundary. For instance, you can see the reflection of light in mirrors.

Refraction - the wave changes direction as it enters a different medium. The change in direction is a result of the wave slowing down or speeding up.

The frequency is the inverse of the period

Seite 2

The Wave Equation Links Wave Speed, Frequency and Wavelength

The speed of the wave is able to be calculated using the following formulae

Light is a type of electromagnetic wave. All EM waves travel with a constant speed in a vacuum of c = 3.00 x 10^8 m/s. The letter c is often used to denote any speed of the wave given the context.