Waves Physical Science

What is a Wave? Movement of energy through a medium by vibrations

Mediums are what? Materials that waves transfer though Types Liquids Air/gases Solid best for sound waves

What moves in a Wave? Energy A wave will move as along as it has energy to carry

Types of Waves Mechanical Waves Surface Waves Is a disturbance in matter that carries energy from one place to another Ex: sound waves Surface Waves Is a wave that travels along a surface separating two mediums Ex: ocean waves (water and air)

Types of Waves Electromagnetic Waves Transverse waves consisting of changing electric fields & changing magnetic fields Ex: x-rays, radio waves

Types of Mechanical Waves Transverse Waves Is a wave that causes a medium to vibrate at right angles to the direction of travel Up and Down motion Ex: Light waves

Wave Parts—Transverse Waves only Crest—highest point on a wave (top of wave) Trough—lowest point on a wave (bottom of wave)

Types of Mechanical Waves Longitudinal Waves Is a wave in which the vibration of the medium is parallel to the direction of travel. Back and forth motion AKA: compressional waves Ex: Sound Waves

Wave Parts—Longitudinal Waves Only Compression—area where particles are close together Rarefaction—area where particles are spread out

Wave Parts Transverse & Longitudinal Waves Wavelength Distance between a point on one wave to the same point on the next wave Transverse Waves Crest to crest Trough to trough Longitudinal Waves Compression to compression

Wave Parts Transverse & Longitudinal Waves Amplitude Max displacement of the medium from resting position Transverse Wave Resting position to crest/trough Longitudinal Wave How compressed the compressions are

Transverse Wave Diagram Crest Trough Wavelength Amplitude Wave Height Resting Position

Longitudinal Wave Diagram Compression Rarefaction Wavelength

Frequency of a Wave Amount of waves that pass a given point in one second Unit= Hertz (Hz) Transverse waves Count the top and bottom pairs Longitudinal waves Count the compressions

Frequency Practice

Frequency & Energy Relationship As frequency increases, the energy in a wave increases They do the same

Frequency & Wavelength Relationship Increase frequency decrease the wavelength of a wave They do the opposite

Wavelength & Energy Relationship Increase the wavelength will decrease the energy They do the opposite

Amplitude & Energy Relationship As the energy of a wave increases, the amplitude increase

Frequency & Period Relationship What is Period? The amount of time it takes one wavelength to pass a point Relationship As the frequency of a wave increase, the period decreases.

Wave Speed = frequency * wavelength Wave Speed Formula Wave Speed = frequency * wavelength Vw = f * λ Vw= wavespeed (m/s) f = frequency (Hz) λ = wavelength (m)

Wave Speed Example Problems A wave has a wavelength of 4 meters and a frequency of 20 Hz. What is the speed of the wave? A wave has a speed of 10 m/s and a length between the crests of 0.5 meters. What is the frequency of the wave?

Speed of Light and Sound Light Waves = 3 x 108 m/s Sound waves = 340 m/s Light travels faster than sound This is why you see lighting before hearing thunder

Wave Interactions How waves behave when they meet a surface, barrier, or another wave Four Basic Types Reflection Refraction Diffraction Interference

Reflection Waves bounce off or back Speed and Frequency does not change Two Types Regular Diffuse Ex: Sonar, Radar

Types of Reflections Regular Diffuse All waves bounce off a surface at the same angle Image is clear Diffuse Waves scatter off a bumpy surface Image is hard to see

Refraction Bending of a wave as it enters a new medium at an angle Direction never changes but wavelength and speed does Ex: waves coming inshore pencil in cup of water Light entering glass

Diffraction Bending of a wave as it moves around an obstacle or passes through a narrow opening Ex: Ocean waves with a barrier Why you hear a parade around a corner Causes light to scatter (reason the sky is blue)

Interference Occurs when two waves overlap and combine together Two Types Constructive Destructive

Constructive Interference When two waves moving in the same direction collide and produce a wave with a larger displacement

Destructive Interference When 2 waves moving in opposite directions, collide and produce a wave with a smaller displacement

Electromagnetic Waves Placed in the electromagnetic spectrum Arranged by wavelength and frequency Can travel through a vacuum Likes no medium

Electromagnetic Spectrum AKA: E-M spectrum Moving from left to Right Wavelength Decrease Frequency Increases

Types of Electromagnetic Waves Radio Waves Longest Wavelength Lowest frequency Types: radio, TV, microwaves, radar Infrared Rays Can’t see with out eyes Used to Detect Heat Ex: heat lamps, night vision goggles

Types of Electromagnetic Waves Red Light Longest wavelength Lowest frequency Violet Light Shortest wavelength Highest frequency Visible Light We Can See White Light can be broken down ROY G BIV

Types of Electromagnetic Waves Ultraviolet Rays Body uses to make vitamin D Causes sunburns Can cause skin cancer We can’t see X-Rays Can pass through skin Cannot go through bones

Types of Electromagnetic Waves Gamma Rays Highest Frequency on E-M spectrum Highest energy on E-M spectrum Found in Space Stopped by 3-m of lead