Waves A wave is a repeated oscillation or disturbance that transfers energy through matter or space. The two primary types of waves are Transverse Longitudinal Transverse Waves In a transverse wave, the energy is moving perpendicular to the matter. matter oscillates in this direction energy travels in this direction matter oscillates in this direction
Transverse Waves B D B' A C equilibrium E Crest is the highest point on a wave. Letter D is a crest. Trough is the lowest point on the wave. Letter E is a trough. Amplitude measures the energy transmitted by the wave. Letter A on the diagram above shows amplitude. Wavelength can be measured from crest to crest or trough to trough. Letter B shows a wavelength. It may also be shown as one full crest plus one full trough. (as indicated by the red dashed line, B') Frequency is a measure of how often a certain part of the medium oscillates. Letter C represents the frequency. Longitudinal Waves Compression is where the wave is most dense, where it carries energy. Rarefaction is the least dense portion of the wave. Amplitude measures the energy transmitted by the wave. Wavelength can be measured from the beginning of one compression to beginning of another compression.
} } Longitudinal Waves higher amplitude more energy compression rarefaction compression lower amplitude less energy wavelength In a longitudinal wave, the motion of the energy is parallel to the motion of the matter. Amplitude is measured differently for longitudinal (compressional) and transverse waves! transverse: longitudinal: If amplitude is doubled, the energy is increased by a factor of four.
Property of Waves Wave Speed (v) The speed of a mechanical wave is constant for any given medium, and v is independent of amplitude and frequency. Medium: the matter that a wave travels through. * Transverse waves travel fastest when they are in outer space, where there is NO medium! Longitudinal waves are faster in a dense medium. Property of Waves Formula for determining the velocity of a wave: v = f λ v = velocity (in m/s) f = frequency (in Hertz, abbreviated Hz); λ = wavelength (in meters) Note: f of wave is determined by the wave source; v is dependent on the medium.
Properties of Waves The energy carried by a wave depends on the amplitude at which the particles of the medium are vibrating. The greater the amplitude, the more energy a wave carries in a given time. The following slides will provide descriptions and illustrations of 5 important wave properties/behaviors you will need to know. Wave Interactions Constructive Interference interference in which individual displacements on the SAME side of the equilibrium position are added together to form the resultant wave. resultant (total wave)
Wave Interactions Destructive Interference interference in which individual displacements on the OPPOSITE side of the equilibrium position are added together to form the resultant wave. resultant (total wave) Wave Interactions Reflection waves bounce from a surface back toward the wave source.
Wave Interactions Refraction waves are refracted when they travel from one medium to another because changing the medium changes wave speed. Refraction is the change in the angle of the wave s direction due to change in medium. Deep Water Shallow Water http://faraday.physics.utoronto.ca/pvb/harrison/flash/waves/refraction/refraction.html Wave Interactions Diffraction waves are diffracted when they bend to move around an obstacle or through a narrow opening. Diffraction is bending caused by an external obstacle.
Wave Interactions Absorption the wave s energy is unable to transmit through the substance and the wave gradually subsides. Sound waves encounter this in the carpeting and upholstery in a theater. (Add illustration in class) Natural frequency: A frequency at which a particular object will oscillate or vibrate. Most objects have multiple natural frequencies. Resonance: Occurs when something causes an object to vibrate at its natural frequency. It results in an increase in amplitude (energy).
Standing Waves Waves that are contained between two boundaries. The boundaries, which are not in motion, are called nodes. The maximum displacement from equilibrium in a standing wave is called an anti node. To determine the harmonic, take the number of nodes in the standing wave and subtract 1. Example: 3 nodes 1 = 2 nd Harmonic 1/2 Wavelength 1 wavelength 1.5 wavelengths 2 wavelengths