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Waves are common!Waves are common!
• Examples of waves:– Sound waves, visible light waves, radio
waves, microwaves, water waves, sine waves, cosine waves, telephone cord waves, stadium waves, earthquake waves, waves on a string, and slinky waves
Queen Elizabeth’s “wave”
WavesWaves
• Anything that moves side to side, back and forth, or front to back and transfers energy from one place to another.
Most common:
Sound waves
Ocean waves
Light waves
How Waves TravelHow Waves Travel
• When waves travel through a solid, liquid, or gas, they are called Mechanical Waves.– Common examples are SOUND waves– The matter which the wave travels through is
called a MEDIUM.
How Waves TravelHow Waves Travel
• Waves that can travel through empty space are called Electromagnetic Waves.– Electromagnetic waves include all light
waves, microwaves, xrays, and radio waves.– Electromagnetic waves do not require a
medium.
• (refer to reference chart)
Shapes of WavesShapes of Waves
• Waves can be described using two models:– Transverse Waves– Longitudinal (also called compression) Waves
• These two labels describe the way in which the wave moves.
Types of WavesTypes of Waves
• Transverse Wave– Particle motion is perpendicular to direction of
energy travel
Orientation Transverse Wave
Orientation Transverse Wave
• Visible light is one type of transverse wave
Types of WavesTypes of Waves
• Longitudinal Waves– Particle motion is parallel to direction of
energy travel
Types of WavesTypes of Waves
• Surface waves are actually combinations of transverse and longitudinal waves– Water waves are a common combination
wave
Other terms to know…Other terms to know…
• Frequency– How many waves per second– Measured in Hertz (Hz)
Frequency & WavelengthFrequency & Wavelength
• The higher the frequency, the lower the wavelength. This relationship is called Non linear, Inversely Proportional.
Check your understanding!Check your understanding!
1. What transfers energy from one place to another?
2. What is matter called that a wave passes through?
3. What are the two waves a wave travels?
4. What are the two shapes of waves?
5. What is the relationship between frequency and wavelength?
Check your understanding!Check your understanding!
1. What transfers energy from one place to another?
2. What is matter called that a wave passes through?
3. What are the two waves a wave travels?
4. What are the two shapes of waves?
5. What is the relationship between frequency and wavelength?
wave
medium
Mechanical and electromagnetic
Transverse and longitudinal
Non linear, Inversely Proportional
Is light a wave or a stream of particles?Is light a wave or a stream of particles?
• The debate has been going on for centuries!
• Light exhibits both particle-like and wave-like behavior
There are unique behaviors of wavesThere are unique behaviors of waves
• Interference
• Polarization
• Diffraction
• These behaviors are dependent on BARRIERS, or anything that interrupts the travel of the wave.
What happens when two waves meet?What happens when two waves meet?
• When two waves meet in the same medium, the waves interfere.
• There are two possibilities– Constructive Interference– Destructive Interference
Types of InterferenceTypes of Interference
• Constructive Interference– Crest meets crest OR trough meets trough– Results in increased AMPLITUDE
Types of InterferenceTypes of Interference
• Destructive Interference– Crest meets trough– Results in decreased AMPLITUDE
Different light sources have different colors contained within them!
Different light sources have different colors contained within them!
Standing WavesStanding Waves
• Standing waves are a result of waves that reflect back upon themselves making a pattern of constructive and destructive interference.
PolarizationPolarization
• Polarization is caused when light is filtered based on the direction of movement of the wave.
Check your understanding!Check your understanding!
1. What is anything that interrupts the pattern of a wave?
2. What is it called when light is passed through a vertical or horizontal filter?
3. What is it called when a wave passes through a narrow slit?
4. What happens during destructive interference?
Check your understanding!Check your understanding!
1. What is anything that interrupts the pattern of a wave?
2. What is it called when light is passed through a vertical or horizontal filter?
3. What is it called when a wave passes through a narrow slit?
4. What happens during destructive interference?
barrier
polarization
diffusion
a crest meets a node and they cancel each other out
How do waves interact with barriers that they can not go around?
How do waves interact with barriers that they can not go around?
• They can be REFLECTED
• They can be ABSORBED
• They can be TRANSMITTED through something called REFRACTION
The Law of ReflectionThe Law of Reflection
• Where is the incident wave?• Where is the reflected wave?• Where is the angle of incidence?• Where is the angle of reflection?
• A• D• B• C
Specular ReflectionSpecular Reflection
What about black and white?What about black and white?
White reflects all colors
Black absorbs all colors (turns energy into heat)
What is Refraction?What is Refraction?
• Refraction is when a wave changes from one medium to another.
• It is caused by the need to change speed in different substances.
Total Internal ReflectionTotal Internal Reflection
Refraction Partial Reflection
Total Internal Reflection!
Check for understanding!Check for understanding!
1. What are the three things light can do when it encounters a barrier it can not go around?
2. What color is an object that absorbs all wavelengths of light?
3. When a wave of light goes from air to water, it is called __________.
4. When 100% of the light wave is reflected due to a critical angle of incidence, it is called __________________.
Check for understanding!Check for understanding!1. What are the three things light can do when it
encounters a barrier it can not go around?
2. What color is an object that absorbs all wavelengths of light?
3. When a wave of light goes from air to water and changes speed, it is called __________.
4. When 100% of the light wave is reflected due to a critical angle of incidence, it is called __________________.
Absorption, reflection, transmission
black
refraction
Total internal reflection
ImagesImages
• Images are formed by transmission of light waves that replicate a barrier (any object).
• Two kinds:– Real
• images are projected onto a screen• Images are upside down
– Virtual• Images are reversed right to left• images are right side up
How do you see?How do you see?
Light REFLECTS off an object
Light REFRACTS through lens of
eye
Light is ABSORBED by the
rods and cones and transmitted to
the brain
HearingHearing
• Hearing is a result of the vibrations of the inner ear bones
• Humans have 3 ear bones: the stirrup, the anvil, and the hammer bones
• Humans can detect sound at a billionth of a centimeter displacement
• Humans can suffer hearing loss at about 1 billion times that threshold
Decibel ScaleDecibel Scale
SourceIntensity
Level# Times
Greater Than TOH
Threshold of Hearing (TOH) 0 dB 100
Rustling Leaves 10 dB 101
Whisper 20 dB 102
Normal Conversation 60 dB 106
Busy Street Traffic 70 dB 107
Vacuum Cleaner 80 dB 108
Large Orchestra 98 dB 109.8
Walkman at Maximum Level 100 dB 1010
Front Rows of Rock Concert 110 dB 1011
Threshold of Pain 130 dB 1013
Military Jet Takeoff 140 dB 1014
Instant Perforation of Eardrum 160 dB 1016
Doppler EffectDoppler Effect
• The Doppler effect is when the sound source is moving– Examples include a blaring horn, sirens– Incoming sound waves are usually louder &
higher frequency– Outgoing waves (after the car has passed),
are lower frequency and softer