Ch. 20 Sec. 1 & 2 The Nature of Waves & Properties of Waves Unit 4 Waves Ch. 20 Sec. 1 & 2 The Nature of Waves & Properties of Waves

Waves We often associate waves with bodies of water, but are there other situations where waves can exist?

Waves wave - a rhythmic disturbance that carries energy without carrying matter matter can move the energy (pass it along), but the matter does not move with the energy

Electromagnetic Waves Types of Waves Mechanical Waves Electromagnetic Waves mechanical waves - use matter to transfer energy produced by the transfer of energy from molecule to molecule the matter the waves travel through is called the medium electromagnetic waves - do not use matter to transfer energy produced by moving electrically charged particles can travel in space/vacuum (no medium needed)

Electromagnetic Waves Mechanical Waves Electromagnetic Waves

Types of Mechanical Waves Transverse Waves Compressional Waves compressional waves - matter in the medium moves in the same direction as the wave travels no crests or troughs ex. sound waves transverse waves - matter in the medium moves at right angles to the direction the wave travels high points are crests & low points are troughs ex. water waves

Compressional MW vs. Transverse MW COMPRESSIONAL MECHANICAL WAVE TRANSVERSE MECHANICAL WAVE

IN SUMMARY…

Electromagnetic Waves Mechanical Waves (medium needed) Transverse (right angle) Compressional (same direction) Electromagnetic Waves (no medium needed)

Amplitude in transverse waves… in compressional waves… amplitude - ½ the distance b/w a crest & a trough in compressional waves… amplitude - varies within a wave amplitude is related to the energy of a wave (higher amplitude = more energy) bright light & loud sounds have higher amplitudes

Wavelength in transverse waves… wavelength - the distance from one crest to the next (or one trough to the next) in compressional waves… wavelength - the distance from one compression to the next (or one rarefaction to the next)

Frequency frequency - # of wavelengths that pass a certain point in 1 sec. unit = hertz (Hz) [wavelengths per second] as wavelength ↑, frequency ↓ (assuming speed is equal) inverse relationship wavelength/frequency determines the color of light & the pitch of sound low frequency = low pitch

Wave Speed mechanical waves, such as sound, travel faster in mediums where atoms are closer together travel faster in solids, slower in liquids, & slowest in gases   electromagnetic waves, such as light, travel faster in mediums where atoms are farther apart travel faster in gases, slower in liquids, & slowest in solids light travels much faster through air than sound light travels at 300 million m/s sound travels at 340 m/s