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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 on a pond - caused by energy being passed from
molecule to molecule = see this as a WAVE
Waves and Energy
Waves only carry ENERGY as they travel
Waves DO NOT carry MATTER
Ex: Boat on a lake
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
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
MECHANICAL WAVES
= Waves that can only travel through matter
-2 TYPES:
-1. TRANSVERSE WAVES
-2. COMPRESSIONAL WAVES
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
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
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
WAVEOn a piece of paper: Explain how sound travels from a
guitar string. What happens when the sound wave
reaches your ear?
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 MOTIONCOOL 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
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.
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.
WAVE PARTSTRANSVERSE
WAVESCREST (high point)
TROUGH
(low point)
WAVE PARTSCOMPRESSIONAL WAVES
Compressions
(crowded/dense
regions)
Rarefaction
(spread-apart/less dense regions)
WAVELENGTH
= Distance between one point on a wave to the next point just like it on
the wave
1 Wavelength
1 Wavelength
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
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
faster
slower
AMPLITUDE
= Related to the amount of ENERGY a wave carries
GREATER AMPLITUDE = GREATER ENERGY CARRIED
Taller wave = More Amplitude
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
Law of Reflection
All Reflected waves obey the following law:
-The Angle of Incidence = The Angle of Reflection
Important TermsINCIDENT BEAM= Light/Sound that 1st strikes an
objectREFLECTED 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)
REFRACTION
=Bending of a wave caused by a change in its speed as it moves from one medium to
anotherWaves 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
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
DIFFRACTION
When an object causes a wave to change direction
and BEND AROUND ITDiffraction V/S Refraction:
Refraction= wave passes through and bends
Diffraction = wave bends around
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?
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
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
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 PhaseWhat happens to the
volume if two sound waves are Out of Phase?
Draw an Example
How could this be used to protect
hearing??
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
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)
SOUND WAVES
All sound is created by VIBRATION
Sound Waves are COMPRESSIONAL
Speed is the SLOWEST thru GASES
Speed is the FASTEST thru SOLIDS
How does Temp Affect Speed?
Increase Temperature = Increase Kinetic Energy =
Increase in Collisions = Increase in Speed of Sound
Ex: 0oC = Speed of sound = 331 m/s
20oC = Speed of sound = 343 m/s
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
DECIBEL SCALE
= dB
-Scale for sound intensity
Ex: 0 dB = faintest sound you can hear
Higher than 120 dB = pain/loss of hearing
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
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
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)
Properties of EM Waves
-All objects emit EM waves
-Increase Temp = Decrease in Wavelength
-Energy carried by EM wave = RADIANT ENERGY
- Provides: Warmth, Sight
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
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
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
EM SPECTRUM
-Thermal energy is produced
-Temperature Increases = Wavelength Decreases
-Ex: Remotes, Computers, Heating food at fast-food restaurants
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
EM SPECTRUM
-Higher Frequencies
-Can enter your skin cells = Cancer
-Can be used to KILL BACTERIA
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
EM SPECTRUM
EM SPECTRUM
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
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
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
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
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
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