LONGITUDINAL WAVES

LONGITUDINAL WAVESDifference between Transverse and Longitudinal waves.

Transverse waves movement of waves right angles to the movement of paricles

Longitudinal waves movement of waves are parallel to movement of particles.Longitudinal waves: the particles oscillate in the direction parallel to the direction that the wave is travelling.Amplitude (r) measured in meters (m)Wavelength () measured in meters (m)Frequency (f) measured in Hertz (Hz)Period (T) measured in seconds (s)Wave speed (v) measured in meters per second (m.s-1).

SOUND WAVESSound waves are Longitudinal wavesSound waves are pressure waves and they transmit energy.Sound waves move the particle in a medium, therefore are mechanical waves. Therefore longitudinal waves cannot pass through a vacuum.Sound waves pass through a gas, but better through a liquid and best through a solid.Sound waves move faster and further through a solid, because the particles in a solid is much closer to one another.The speed of sound increases with an increase in temperature. At 0C sound travels through air at 331 m.s-1 and at 20C the speed increases to 343 m.s-1.(DO ACTIVITY 1 no 1-6 pg 117)Pitch, Loudness and Quality of soundPitch of soundHigh or lowness of sound is called pitch.Pitch dependent on frequencyThe higher the frequency, the higher the pitch.The human ear hear sounds with frequencies between 20 Hz and 20 000 Hz (audible range)

LOUDNESS OF SOUNDSThe loudness of a sound is related to the intensity of a wave. (measurement of energy transported by the wave)The amplitude of a wave is the maximum distance that the vibrating particles moves from their rest position .The human ear hear sounds with frequencies between 20 Hz and 20 000 Hz (audible range)Loudness depends on both the amplitude and frequency of a sound wave.

Quality of soundThere is a difference between the sounds of a middle c on a piano and the same note played on a flute. Musical instruments play a variety of frequencies. Our brains interpret regular vibrations as musical sounds.A sound with a great number of frequencies is a discordant noise.A tuning fork produces a note of a single frequency.

ULTRA SOUNDFrequencies of 20 000 Hz (20 kHz)Not audible to the Human ear, but many animals can like dogs (50 kHz) and bats (100 kHz).Medically ultrasound is used in sonar scans, to detect and destroy tumours and gallstones, measure blood flow through organs.

ELECTROMAGNETIC RADIATIONWAVE-PARTICLE DUALITYElectromagnetic radiation shows wave-like behaviour (such as diffraction, interference and polarisation) and particle-like behaviour.

Piano