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

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

Types of Mechanical Waves A.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

Types of Mechanical Waves B.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—Transverse Waves only Crest—highest point on a wave (top of wave) Trough—lowest point on a wave (bottom of wave)

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 A.Crest B.Trough C.Wavelength D.Amplitude E.Wave Height F.Resting Position

Longitudinal Wave Diagram A.Compression B.Rarefaction C.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 Formula Wave Speed = frequency * wavelength V w = f * λ V w = wavespeed (m/s) f = frequency (Hz) λ = wavelength (m)

Wave Speed Example Problems 1.A wave has a wavelength of 4 meters and a frequency of 20 Hz. What is the speed of the wave? 2.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 10 8 m/s Sound waves = 340 m/s Light travels faster than sound This is why you see lighting before hearing thunder

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

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

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

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

Wave Interactions How waves behave when they met 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 – 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