Waves, sound & 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 don’t carry the medium itself with them.

Waves are created when a source of energy causes a medium to vibrate.

Types of wavesTransverse: 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 WavesThe 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 wavesAmplitude: 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’dWavelength: distance between two

corresponding parts of a wave.

Properties of waves Ct’dFrequency: the number of complete waves

that pass a given point in a certain amount of time. Measured in Hertz Hz

Properties of waves Ct’dSpeed: 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 SoundDepends 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 SoundIntensity: 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 SoundFrequency: the number of vibrations that

occur per second. Most people hear 20 Hz to 20,000 HzUltrasound: frequencies above the normal

range of hearing.Infrasound: Sounds with frequencies below

the normal range of hearing.

Properties of SoundPitch: 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.

Doppler Effect

Electromagnetic Waves