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Published byAngela Gordon Modified over 5 years ago

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Waves A wave is a rhythmic disturbance that carries energy through matter or space.

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**Two Categories of Waves**

Mechanical Waves A wave that requires a medium (matter). Electromagnetic Waves (Coming Soon, Chapters 16 – 19)

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**Types of Mechanical Waves**

Transverse A wave that vibrates perpendicular to the motion of the waves.

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**Types of Mechanical Waves**

Longitudinal A wave that vibrates parallel to the motion of the wave.

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**Types of Mechanical Waves**

Surface A wave that is a combination of both transverse and longitudinal waves (overall motion is circular).

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**Wave Properties Amplitude – maximum displacement from equilibrium.**

The crest (compression) is highest point of the wave and the trough (rarefaction) is the lowest point of the wave. Wavelength – The distance of one complete wave cycle (oscillation).

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Wave Measurements Frequency (f) – Number of complete oscillations in one second; measured in Hertz. Period (T) – The time elapsed in one complete wave cycle (oscillation). Wave speed (v) – The product of the wavelength and frequency or, the wavelength divided by the period.

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Wave Behavior Reflection – the bouncing back of a wave as it encounters a boundary. Fixed point reflection Free boundary reflection

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Wave Behavior Diffraction – the spreading of waves around a barrier or object.

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Wave Behavior Refraction – the change in the direction of a wave as it enters a different medium.

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**Wave Behavior Interference**

Principle of Superposition – the combination of two or more waves into a single wave. Constructive interference Destructive interference Standing waves (nodes & antinodes)

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Sound Waves Sound waves are longitudinal pressure variations that are transmitted through matter. Sound is produced by vibrating objects.

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**Properties of Sound Waves**

Sound Level (loudness) The amplitude of a sound wave. Measured in decibels (dB). A 20 dB increase equals a 10 time increase in pressure amplitude. Pitch Describes the frequency of vibrations. More vibrations = higher pitch; less vibrations = lower pitch.

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The Doppler Shift The apparent change in the pitch of a sound as it moves towards or away from an observer Pitch increases as a sound moves toward an observer. Pitch decreases as a sound moves away from an observer.

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**Sound & Music Closed-pipe resonators**

A resonating tube (column) with one closed end and one open end. Minimum resonance frequencies occur at one-fourth of the wavelength, then at half-wavelength intervals. Column lengths of (1/4)λ, (3/4)λ, (5/4)λ, etc., will result in resonance.

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**Sound & Music Open-pipe resonators**

A resonating tube (column) with both ends open. Minimum resonance frequencies occur at one-half of the wavelength, then at half-wavelength intervals. Column lengths of (1/2)λ, λ, (3/2)λ, 2λ, etc., will result in resonance.

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**Sound & Music Fundamental (f1) Harmonics Octave**

The lowest frequency of resonance. Harmonics Higher frequencies that are multiples of the fundamental frequency. Octave The difference in frequency of two musical notes with ratio of 1:2.

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**Sound & Music Beats Oscillations in wave amplitude.**

The frequency of the beat is the magnitude of the difference between the two frequencies.

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