Waves

Waves3 Types of Waves

Mechanical Waves: Wave motion that requires a medium (ie. water, sound, slinkies, …)

Electromagnetic Waves: No medium is needed (light, radio waves, x-rays,…)

Matter Waves: Electron and other particles show wave like behavior under certain conditions

Physics Definition: A vibration or oscillation that transfers energy.

The Energy of Waves

Nicknamed Galloping Gerdie

Mechanical WavesClassified by how they

displace the medium in which they travelTransverse

waves: Medium is displaced perpendicular to the direction of the wave

Longitudinal Waves: Medium is displaced parallel to the direction of the waveSurface

Waves: Medium is displaced both perpendicular and parallel to the direction of the wave

Particles of a medium move in response to a passing wave but do not move along with the wave

Properties of a Wave

f

Amplitude: Displacement from the line of equilibrium to the height of a crest or trough.

Crest: The highest displacement from the line of equilibrium.

Trough: The lowest displacement from the line of equilibrium.

Wavelength: Shortest distance between points of a wave, where the wave pattern repeats itself

Wave speed: Speed at which a wave travels through a medium. It depends solely on the properties of the medium. Independent of the wavelength or the frequency

Frequency: The number of waves that pass a given point in a second of time.

v f

Line of equilibrium

RefractionReflectionDiffraction

ReflectionWaves may “bounce off” Waves may “bounce off”

barriers.barriers.Law of Reflection = The angle of incidence equals the angle of reflection

Ray DiagramsDiagrams that show the direction

of a wave front in two or three dimensions

Normal

RefractionWaves may change when they pass from one medium to another.

Wave length and wave velocity may change while frequency remains constant

Waves also may change direction – that change in direction of waves at the boundary between the two different media is known as refraction

Refraction of Light Waves

Ray Diagram of Refraction

i

r

i

= angle of incidence

r= angle of refraction

DiffractionDiffraction is the bending of

waves around a barrier

Interference of WavesPrinciple of Superposition – The displacement of a medium caused by

two or more waves is the algebraic sum of the displacements caused by the individual waves.

The result of superposition is interference

Constructive InterferenceDestructive Interference

Two kinds of Two kinds of interference can occur interference can occur

when waves meetwhen waves meet

Standing vs Traveling Waves

A traveling wave is a disturbance which is created by a vibrating object and subsequently travels through a medium from one location to another, transporting energy as it moves. The most commonly observed traveling wave is an ocean wave.

Standing wave patterns are always characterized by an alternating pattern of nodes and antinodes.

Standing wave patterns are also characterized by antinodal positions - positions along the medium that undergo maximum displacement from a high upward displacement to a high downward displacement. Antinodes are the result of a crest meeting a crest to form a supercrest and a trough meeting a trough to form a supertrough.

Such positions are referred to as nodal positions or nodes. Nodes are the result of the meeting of a crest with a trough; this form of interference is known as destructive interference and leads to a point of "no displacement." A node is a point of no displacement.

Standing vs Traveling Waves

A standing wave pattern is a pattern which results from the interference of two or more waves along the same medium. All standing wave patterns are characterized by positions along the medium which are standing still.

Reflection

Refraction

Diffraction

Interference

ConstructiveDestructiveStanding Wave

Traveling Wave