Waves, sound & Light

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# Waves, sound & Light - PowerPoint PPT Presentation

Waves, sound &amp; Light. Wave: a disturbance that transfers energy from place to place. The material through which a wave travels through is called a medium . Waves that require a medium are called mechanical waves . The waves donâ€™t carry the medium itself with them.

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### Waves, sound & Light

• The material through which a wave travels through is called a medium. Waves that require a medium are called mechanical waves. The waves don’t carry the medium itself with them.
• Waves are created when a source of energy causes a medium to vibrate.
Types of waves
• Transverse: move the medium at right angles to the direction in which the waves are traveling.
• Longitudinal /Compressional: move particles of the medium parallel to the direction in which the waves are traveling.
• Surface waves: combinations of transverse and longitudinal waves. They occur at the surface between two mediums, such as water and air. Causes water to move in a circle.
Transverse Waves
• The highest points are called the crest, and the lowest are called the troughs.
Longitudinal / Compressional:
• The parts where the coils are close together are called compressions. The parts where the coils are spread out are called rarefactions.
Properties of waves
• Amplitude: the maximum distance the particles of the medium carrying the wave move away from rest position. It is a direct measure of energy.
Properties of waves Ct’d
• Wavelength: distance between two corresponding parts of a wave.
Properties of waves Ct’d
• Frequency: the number of complete waves that pass a given point in a certain amount of time. Measured in Hertz Hz
Properties of waves Ct’d
• Speed: Waves in different mediums travel at different speeds. In addition the speed is related to the amount of pressure and temperature.
Sound
• Sound waves carry energy through a medium without the particles of the medium traveling along. A common medium is air. It travels as a longitudinal wave.
• Sound waves can bend around a barrier, diffraction such as hearing around a corner.
Speed of Sound
• Depends on elasticity, density , and temperature.
• Elasticity: Travels more quickly in things that have more elasticity. The speed is faster in a solid, then liquid then gas.
• Density: faster in the LEAST dense items.
• Temperature: faster in higher temperatures.
Properties of Sound
• Intensity: the amount of energy the wave carries per second through a unit area. Measured in W/m²
• Loudness: what you actually hear. Measured in dB decibels. Each 10 dB increase represents a tenfold increase in intensity.
Properties of Sound
• Frequency: the number of vibrations that occur per second.
• Most people hear 20 Hz to 20,000 Hz
• Ultrasound: frequencies above the normal range of hearing.
• Infrasound: Sounds with frequencies below the normal range of hearing.
Properties of Sound
• Pitch: description of a sound of how high or low the sound seems to a person. It depends on the frequency.
• High frequency sound waves have a high pitch while low pitch is made from a low frequency.