Waves Wave a rhythmic disturbance that transfers energy

Waves • Wave: a rhythmic disturbance that transfers energy through matter or space. – Carries energy without carrying matter from place to place.

Classifying Waves can be either Electromagnetic or Mechanical. • Electromagnetic Waves: waves capable of transferring energy through a vacuum. – Ex. Light waves • Mechanical Waves: waves that can only travel through a medium. • Medium: matter through which a wave travels through; can be solid, liquid, or gas. – Ex. Sound waves, water waves

Classifying Waves can be either Transverse or Longitudinal. • Transverse: matter in the medium moves back and forth at right angles to the direction that the wave is traveling. – Particle motion is perpendicular to wave motion. – Ex. Electromagnetic waves, vibrations in string instruments, ripples of surface of water. • Longitudinal: (aka compressional waves) matter in the medium moves back and forth in the same direction that the wave is traveling. – Particle motion is parallel to wave motion. – Ex. Sound waves, ultrasounds, waves made with a slinky.

Labeling Parts of Waves In transverse waves… • Crest: (aka peak) • Trough: lowest highest points of a transverse wave. Normal resting position of wave

Labeling Parts of Waves In longitudinal waves… • Compression: where particles are pushed together in a longitudinal wave. Compression • Rarefaction: where particles are spread apart in a longitudinal wave. Rarefaction

Measuring Waves • Amplitude: the amount of energy carried by a wave. Transverse Waves The height of the wave Longitudinal Waves The amount of compression in the wave

Measuring Waves • Wavelength: (�� ) the distance between one point on a wave and the nearest point just like it. Longitudinal Waves – Measured in m Transverse Waves Crest to crest, or trough to trough Compression to compression, or rarefaction to rarefaction

Measuring Waves • Period: (T) the amount of time it takes one wavelength to pass a point. – Measured in s • Frequency: (�� ) the number of waves that pass a given point in one second. – Measure in Hertz (Hz) • I Hertz = 1/s or s-1 T = 1 Frequency and period have an inverse �� relationship. �� =1 T

Measuring Waves • Frequency and wavelength also have an inverse relationship. – The higher the frequency, the shorter the wavelength. – The lower the frequency, the longer the wavelength.

Measuring Waves • Wave speed: (v) how fast the wave travels. – Measured in m/s – Speed is dependent on the type of wave and properties of the medium the wave is traveling through. • Mechanical waves (like sound): must travel through particles, therefore travel fastest through solids, then liquids, then gases, due to the closeness of the particles. – Also travel faster through warmer mediums, because particles collide more. • Electromagnetic waves (like light): do not need a medium, therefore travel fastest through a vacuum, and slowest through solids.

Measuring Waves To calculate wave speed: v = ���� v = velocity Measured in m/s = frequency �� = wavelength �� Measured in m Measured in Hz Example #1: What is the speed of a wave with a wavelength of 2 m and a frequency of 3 Hz? λ=2 m f = 3 Hz v=? v = (2)(3) v = 6 m/s v = ����

Example #2 A wave is traveling at a speed of 12 m/s and its wavelength is 3 m. Calculate the wave’s frequency and period. v = 12 m/s λ=3 m f=? T=? v=λf λ f=v λ λ T=1 �� f = 12 3 T=1 4 f = 4 Hz T = 0. 25 s

Practice Time 1. A tuning fork has a frequency of 280 Hz and the wavelength of the sound produced is 1. 5 m. Calculate the velocity of the wave. Answer: v = 420 m/s 2. A wave is moving toward shore with a velocity of 4 m/s. If its period is 0. 4 s, what is its wavelength? Answer: �� = 1. 6 m