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What is a Wave?? Wave = Repeating disturbance/movement that TRANSFERS ENERGY through MATTER or SPACE ENERGY can travel in the form of a WAVE Ex: Ripples.

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Presentation on theme: "What is a Wave?? Wave = Repeating disturbance/movement that TRANSFERS ENERGY through MATTER or SPACE ENERGY can travel in the form of a WAVE Ex: Ripples."— Presentation transcript:


2 What is a Wave?? Wave = Repeating disturbance/movement that TRANSFERS ENERGY through MATTER or SPACE ENERGY can travel in the form of a WAVE Ex: Ripples on a pond - caused by energy being passed from molecule to molecule = see this as a WAVE

3 Waves and Energy Waves only carry ENERGY as they travel Waves DO NOT carry MATTER Ex: Boat on a lake

4 What Produces Waves?? All waves are produced by VIBRATIONS Vibration = causes things to move up/down or back/forth When vibrations stop = energy stops = waves stop

5 What is a MEDIUM?? Medium = the matter that waves travel through -Can be: SOLID, LIQUID, or GAS or a combo of the three Medium for SOUND WAVES = Medium for OCEAN WAVES = AIR WATER Do all waves travel through a medium?? NO! Radio and light waves can travel through space

6 MECHANICAL WAVES = Waves that can only travel through matter -2 TYPES: -1. TRANSVERSE WAVES -2. COMPRESSIONAL WAVES

7 TRANSVERSE WAVES MATTER moves BACK and FORTH at RIGHT ANGLES to the direction that the wave travels Ex: Ocean Waves move horizontally towards the beach Water within the wave moves up and down (at a right angle to the wave) Draw an example and label with arrows

8 COMPRESSIONAL WAVES Matter moves BACK and FORTH in the SAME DIRECTION the wave travels AKA: LONGITUDINAL WAVES Ex: SLINKY Draw an example and label with arrows

9 SOUND WAVES = COMPRESSIONAL WAVES -Noise pushes nearby air molecules together by their VIBRATIONS (just like in a slinky) -The compressions travel through the air to make a WAVE On a piece of paper: Explain how sound travels from a guitar string. What happens when the sound wave reaches your ear?

10 WATER WAVES = TRANSVERSE WAVES (but not completely) WHAT?? Water moves up/down as the wave moves horizontally but the water also moves a short distance back and forth horizontally The combo of the up/down and side/side motion causes water to move in CIRCLES = THUS stuff on the surface absorbs this energy and bobs in a CIRCULAR MOTION COOL FACT: Wind causes most ocean waves. The size of the wave depends on the wind speed, distance over which the wind blows,and time which the wind blows

11 SEISMIC WAVES = Combo of COMPRESSIONAL and TRANSVERSE WAVES -Travel through Earth and along Earth’s surface -Carry energy with them -Objects on Earth’s surface ABSORB some of this energy = MOVE and SHAKE -MORE THE CRUST MOVES = MORE ENERGY RELEASED Turn to pg. 294 in your book. Read the article.

12 Questions on Reading pg 294 1.What happens to the surface area of water exposed to the wind as waves build up? 2. How does this affect the waves? The surface area INCREASES The greater the surface area means that there is more contact area between the air and water, providing an increased area to which energy may be transferred.


14 WAVE PARTS COMPRESSIONAL WAVES Compressions (crowded/dense regions) Rarefaction (spread-apart/less dense regions)

15 WAVELENGTH = Distance between one point on a wave to the next point just like it on the wave 1 Wavelength

16 FREQUENCY AND PERIOD FREQUENCY: # of wavelengths that pass a fixed point each second - expressed in Hertz (Hz) PERIOD: Time it takes one wavelength to pass a fixed point - expressed in Seconds (s) As FREQUENCY INCREASES = PERIOD DECREASES As FREQUENCY INCREASES = WAVELENGTH DECREASES

17 WAVE SPEED Wave Speed = v Wavelength = lambda Frequency = f Speed (m/s) = frequency (Hz) X wavelength (m) V = f Light waves are _________ than Sound waves Sound waves travel _______ in solids and liquids than in gasses Light waves travel _______ in solids and liquids than in gases/space faster slower

18 AMPLITUDE = Related to the amount of ENERGY a wave carries GREATER AMPLITUDE = GREATER ENERGY CARRIED Taller wave = More Amplitude

19 REFLECTION = When a wave hits an object and BOUNCES off of it -All types of waves can be reflected Ex: Seeing yourself in a mirror or Echos

20 Law of Reflection All Reflected waves obey the following law: -The Angle of Incidence = The Angle of Reflection

21 Important Terms INCIDENT BEAM= Light/Sound that 1 st strikes an object REFLECTED BEAM= Beam bouncing off an object NORMAL= The line perpendicular to the surface of the object ANGLE OF INCIDENCE= Angle formed by Incident Beam and Normal (i) ANGLE OF REFLECTION= Angle formed by Reflected Beam and Normal (r)

22 REFRACTION =Bending of a wave caused by a change in its speed as it moves from one medium to another Waves change speed when they change mediums Waves traveling at an angle, change direction (bend), when they change mediums Increase change in speed = Increase in Bending of Wave

23 REFRACTION Wave enters a medium that slows it down = Bends TOWARD the normal Wave enters a medium that speeds it up = Bends AWAY from the normal

24 DIFFRACTION When an object causes a wave to change direction and BEND AROUND IT Diffraction V/S Refraction: Refraction= wave passes through and bends Diffraction = wave bends around

25 Diffraction and Wavelength 1.Obstacle SMALLER than wavelength = wave BENDS AROUND 2.Obstacle LARGER than wavelength = Less bending 3.Obstacle WAY LARGER than wavelength = NO Diffraction = Obstacle passes a SHADOW AM = longer wavelengths than FM. So which gives better reception in the mountains?

26 INTERFERENCE = When two or more waves overlap and combine to form a new wave -New wave exists only while the two waves overlap -Two types of Combination 1.Constructive Interference 2.Destructive Interference

27 CONSTRUCTIVE INTERFERENCE Waves ADD TOGETHER -Happens when two or more crests or compressions arrive at the same time and OVERLAP -Amplitude of new wave = Sum of the old wave amplitudes -Waves in Constructive Interference = In Phase What would happen to a the volume of two sound waves were In Phase? Draw an Example

28 DESTRUCTIVE INTERFERENCE Waves SUBTRACT from each other -Happens when a crest and a trough meet up or a compression and rarefaction meet up -Amplitude of new wave = Difference between the amplitudes of the old waves -Waves in Destructive Interference = Out of Phase What happens to the volume if two sound waves are Out of Phase? Draw an Example How could this be used to protect hearing??

29 STANDING WAVES = Special type of wave pattern that forms when waves equal in wavelength and amplitude, traveling in opposite directions, continue to interfere -Creates a pattern of crests/troughs that don’t seem to move = “Stands Still” -Nodes = places where the two waves cancel = stay in the same place

30 RESONANCE = Process by which an object is made to vibrate by ABSORBING energy at its natural frequency -All objects have a natural frequency - If enough energy is absorbed, the object can vibrate so strongly = breaks! Ex: Tuning Forks Wine glass (mythbusters)

31 SOUND WAVES All sound is created by VIBRATION Sound Waves are COMPRESSIONAL Speed is the SLOWEST thru GASES Speed is the FASTEST thru SOLIDS

32 How does Temp Affect Speed? Increase Temperature = Increase Kinetic Energy = Increase in Collisions = Increase in Speed of Sound Ex: 0 o C = Speed of sound = 331 m/s 20 o C = Speed of sound = 343 m/s

33 LOUDNESS and INTENSITY OF SOUND LOUDNESS = Perception of Intensity Increase the ENERGY in the wave = Increase Loudness INTENSITY = Amount of energy flowing through an area in a specific amount of time Decreases as Distance Increases

34 DECIBEL SCALE = dB -Scale for sound intensity Ex: 0 dB = faintest sound you can hear Higher than 120 dB = pain/loss of hearing

35 PITCH = How HIGH or LOW a sound seems to be -Related to the FREQUENCY OF THE WAVE -High Pitch = High frequency -Low Pitch = Low frequency Ex: Whistle = 1000 Hz Thunder = 50 Hz

36 DOPPLER EFFECT = Change in Pitch/frequency due to moving the wave source Ex: Race Car Track Car comes toward you = high pitch Car goes away from you = low pitch

37 ELECTROMAGNETIC WAVES -Can travel through SPACE (do not need matter) -Made by: VIBRATING ELECTRIC CHARGES and Magnetic Fields -TRANSVERSE WAVE (Electric field and Magnetic field are perpendicular to each other)

38 Properties of EM Waves -All objects emit EM waves -Increase Temp = Decrease in Wavelength -Energy carried by EM wave = RADIANT ENERGY - Provides: Warmth, Sight

39 Properties of EM Waves -Speed of EM Waves = 300,000 km/s in vacuum of space -AKA: “Speed of Light” -”Nature’s Speed Limit” = Nothing is faster! -Speed changes depending on medium: -Slowest in Solids -Fastest in Gases

40 Properties of EM Waves Wavelength = Distance from crest to crest Frequency = # of wavelengths passing a pt in 1 sec RELATIONSHIP BETWEEN WAVELENGTH AND FREQUENCY: F increases = wavelength decreases

41 EM SPECTRUM Range of EM wave frequencies Includes: -Low-Frequency waves -Includes the following types: A.Microwaves = ex: cooking food B.Radar (Radio Detecting And Ranging) = ex: Speed, tracking C. MRI (Magnetic Resonance Imaging) = ex: Diagnose Illness, pictures of body

42 EM SPECTRUM -Thermal energy is produced -Temperature Increases = Wavelength Decreases -Ex: Remotes, Computers, Heating food at fast-food restaurants

43 EM SPECTRUM -Range of EM waves you can detect with your eyes -Color = eyes react differently to different wavelengths = you see color -Blue = Short Wavelength -Red = Long Wavelength -White = All wavelengths of color

44 EM SPECTRUM -Higher Frequencies -Can enter your skin cells = Cancer -Can be used to KILL BACTERIA

45 EM SPECTRUM -Shortest wavelengths and Highest frequencies -Gamma Rays are shorter than X rays -X rays = can provide images of organs -Gamma Rays can kill and damage cells



48 LIGHT WAVES - To see an object, light must REFLECT off of the object and hit your eye - Opaque Objects = Absorb and reflect light/NO light passes through (you can’t see through these objects) - Translucent Objects = Allow some light to pass through but you can’t see through it clearly - Transparent Objects = Transmit almost all light so you can see clearly through them

49 REFLECTION OF LIGHT -Light waves obey the LAW OF REFLECTION - If all objects reflect light, then why can you see yourself in a mirror but not in a brick wall?? Brick Walls have BUMPY surfaces which reflect light in all directions whereas a mirror is very smooth and reflects light mostly back to your eye in one direction

50 REFRACTION OF LIGHT All objects have an INDEX OF REFRACTION = indicates how much the speed of light is reduced when it travels through the object - Higher the Index of Refraction = The more the speed is slowed down

51 REFRACTION OF LIGHT PRISMS- Bend light -Produce color because the light traveling through the prism bends based on the wavelength of light - Sunlight = White Light = Has all wavelengths - Longer wavelengths are refracted less = Red bends the least - Rainbows = Water droplets do the same thing as a prism

52 COLOR -Color of an object depends on the wavelength the object REFLECTS -Ex: Red Apple = Reflects RED/Absorbs everything else -Black = Absorbs all wavelengths FILTERS -Color of a filter = color of light it reflects

53 MIXING COLORS PIGMENTS = colored material used to change the color of other substances -Results from the different wavelengths of light the pigment reflects -All colors can be made by mixing 3 color of light 1.Red 2.Blue 3. Green Primary Colors of Light

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