Topic 4 - Waves

Definitions for Topic 4 - Oscillations and Waves: 4.1 - Oscillations 4.2 - Travelling waves 4.3 - Wave characteristics 4.4 - Wave behaviour

Time period

Time period

The time it takes for the object to complete one full oscillation

Frequency

The number of cycles or oscillations completed per unit time

Simple harmonic motion

1. The magnitude of the force that acts on the object is proportional to the displacement from a fixed point

2. The direction of the force is always toward the fixed point

Transverse wave

A traveling wave where the oscillations are perpendicular to the direction in which the wave travels

Longitudinal wave

A traveling wave where the oscillations are parallel to the direction in which the wave travels

Wavefront

A surface traveling with the wave. It is perpendicular to the direction in which the wave travels and contains points that oscillate in phase

Ray

An arrow showing the direction in which the wave transfers energy. It is perpendicular to the wavefront

Intensity

The power per unit area carried by a wave

Superposition

When two or more waves travel through the same medium at the same time, the displacement of the medium is the sum of the individual wave displacements

Polarisation

Unpolarized light: the electric field vector vibrates in all directions in the plane that is perpendicular to the direction in which the beam is traveling

Polarization: the direction of the electric field vector vibrations is restricted

Plane polarised light: the direction of electric field vector vibrations stays constant over time

Refractive index (n)

The ratio of the speed of electromagnetic waves in a vacuum to the speed of electromagnetic waves in the medium

Critical angle

The angle when the refracted ray travels along the boundary

Only exists when light passes from a more optically dense to a less optically dense medium

Total internal reflection

When the angle of incidence is larger than the critical angle, the incident ray is completely reflected into the original medium

Standing wave

When two traveling waves that have the same amplitude, frequency, and speed travel in opposite directions and superpose, a standing wave is formed

Harmonic

Two fixed points: wavelength= 2L/n

One fixed and one free: wavelength= 4L/n

Two free points: wavelength= 2L/n