Waves I. Nature of a Wave

A. Vibrations and SHM 1. Defining Vibrational and Harmonic Motion Vibration : in a general sense, anything that switches back and forth, to and fro, side to side, in and out, off and on, loud and soft, or up and down is vibrating. A vibration is a wiggle in time. Wave : a wiggle in both space and time is a wave. A wave extends from one place to another. Vibrations and waves: the source of all waves is something that is vibrating. Waves are propagations of vibrations throughout space. repeats Harmonic motion occurs when a vibration repeats and is converted (no energy input is needed to continue the motion)

2. Measuring SHM Cycle : A cycle is a unit of motion that repeats. A cycle is used to measure properties of vibrations

Amplitude : The amplitude of a wave refers to the distance from the equilibrium point (or ½ the distance from highest to lowest point of vibration) Frequency : The frequency of a wave refers to how many “waves” pass by a point in a given amount of time (usually a second) o Unit: # cycles/second (or later #waves/s) which is aka a Hertz (Hz) o A Hertz is the same thing as s -1 or 1/s Period : The period of a wave is the time to make one complete cycle. Period, being a time, is measured in units of time such as seconds, hours, days or years. o Unit: # seconds/cycle (or later we will use #seconds/wave)

Graphing harmonic motion When oscillations are small, the motion is called simple harmonic motion (shm) and can be described by a simple sine curve. See animation

. Definition of wave A. Definition of wave A disturbance which travels through a medium from one point in space to the others.

B. Categories of Waves Waves are classified into different types according to their natures :

1. Classification based on direction of vibration— direction of motion according to the direction of vibration, waves are classified into : (a) Transverse wave; (b) Longitudinal waves.

a. Longitudinal Waves a. Longitudinal Waves A wave in which the motions of the matter particles are in the same direction as the wave propagation. Examples Sound, or a spring oscillating up and down

b. Transverse Waves The waveform appears in the shape of sine curve. A wave in which the motions of the matter particles are perpendicular to the direction of propagation of the wave itself. Water waves, pulse in a stretched string,transverse wave demonstrator. Examples