# Waves.

## Presentation on theme: "Waves."— Presentation transcript:

Waves

What is a wave?  - a repeating disturbance or movement that transfers energy through matter or space Examples: ocean waves light sound

Waves travel through matter - this is called the MEDIUM
Mediums can be - solid  (earth) - liquid (water) - gas  (air) Light and radio waves travel through space and do not need a medium.

Movie Trivia. Each of these has something to do with waves
1.  This movie from 1991 stars Keanu Reeves and Patrick Swayze as a pair of surfers who also rob banks. 2.  In 1998, a meteor hits the earth and creates a huge wave.  The tagline for this movie was "The coast is toast."

Transverse Waves - medium moves at a right angle to the direction of the wave (like in the ocean)
Compression waves - medium moves along the same direction as the wave, visualize a coiled spring.

Sound waves are compressional waves caused by air molecules vibrating, like when a door slams
Sound waves can also travel through other mediums, like earth and water

RAREFACTION = area of wave where it is less compressed
You can use a Slinky to get a good idea of how compressional waves, such as sound, move. Stretch a Slinky out and then give one end a good strong knock or jiggle. This will push the coils near your hand into the ones next to them, which will be pushed into the next and the next and so on, all the way to the other end. At the other end, the compression will rebound and move back in the other direction. Thus a "compression" moves back and forth. RAREFACTION = area of wave where it is less compressed

Winds continue to push on the water and generate waves, the waves trap more wind and get bigger and bigger.  The size of the wave depends on wind speed.

Shallow water causes wave to "break"
Other factors can reduce the size of a wave before it lands, such as reefs or islands. A steep drop off will make a larger wave.

The moon doesn't cause waves, but it does cause tides.
A tide is the rise and fall of the ocean and is based on the sun, moon, the earth's rotation

Wind and Rogue Waves, match these shipwreck / disaster at sea stories.
1. A rogue wave capsizes a cruise ship. People who survived must climb their way to the surface because the ship is floating upside down. 2.  Not caused by a wave exactly..but this ship was wrecked because it ran into a floating iceberg. 3.  Who was the Greek God who held dominion over the ocean and the waves? 4.  This villain's ship moved under the waves.   He chased Jack Sparrow throughout the second Pirates movie.  What as his name? The Poseidon The Titanic Poseidon Davy Jones

What is a rogue wave? Deadliest Catch Video
also known as freak waves, monster waves, killer waves, extreme waves, and abnormal waves are relatively large and spontaneous ocean surface waves that occur far out in sea. Deadliest Catch Video

We perceive these waves as earthquakes.
Seismic Waves - waves that occur on the crust of the earth.  They can cause structures to collapse We perceive these waves as earthquakes. Earthquakes can cause a TSUNAMI

Quick Review Type of Wave Where it Occurs What does it do?
Seismic Waves Sound Waves Rogue Waves Ocean Waves

The Parts of a Transverse Wave
The high part of the wave is the CREST The low part of the wave is the TROUGH Wavelength = the distance from one point of the wave to the next point

This is not on your notes...
Practice Labeling

More Practice CREST AMPLITUDE WAVELENGTH TROUGH

Parts of a Wave as explained by surfers
What type of wave is best for beginners? _______________ What type is for experienced surfers? _________________

The Parts of a Transverse Wave
FREQUENCY =  number of waves that pass a point in a second Frequency is measured in hertz (Hz) Each wave has a PERIOD, which is the amount of time it takes for one wavelength to pass a point

This makes the wavelength SHORTER high frequency = short wavelength
If you make transverse waves by moving a rope up and down, you can increase the frequency by moving the rope faster. This makes the wavelength SHORTER high frequency = short wavelength low frequency = long wavelength

Wave Speed - how fast a wave travels
Speed (m/s) =  frequency (Hz)  x wavelength (m) Greek letter lambda is used to represent wavelength

Wave Amplitude Amplitude is related to the amount of energy a wave carries. Tighter packed coils of the slinky will cause greater energy. In the rope, raising the hand higher and causing "bigger" waves increases the amplitude Amplitude = height of wave

QUIZ  TIME (only covers first half of notes)

1.  The material a wave passes through (such as water or air) is called the _______________________
2.  What type of wave is this?           ________________ 3.  What causes waves in the ocean?  _______ Label the parts of the wave. 4.  Wavelength ____ 5.  Crest ____ 6.  Amplitude ____ 7.  Trough ____

8.  Which of these waves has a higher frequency?
9.  Frequency is measured with what unit? 10.  Write the equation used to calculate wave speed? B A

Light and sound both travel in waves. Both can be reflected!
Wave Reflection Waves bounce off objects and reflect back the direction they came. With sound waves, this creates an echo. Light and sound both travel in waves. Both can be reflected!

The Law of Reflection uses math to determine the angle a wave (light or sound) will reflect.
You can witness this law in action using a laser pointer and a mirror

If the arrow is a flashlight beam, what is its angle of reflection?
Geometry Attack If the arrow is a flashlight beam, what is its angle of reflection? 120 °

What is REFRACTION Why does this straw appear broken at the point it enters the water? Refraction is the bending of a wave caused by a change in speed as it moves from one medium to another.

Light refraction can make it very difficult to catch fish in water, they are not actually where they appear to you...

What causes a rainbow? Light passes through a prism
Water molecules can act as a prism.   This is why you see rainbows after it rains. Visible light is separated into its different wavelengths (7) R.O.Y.G.B.I.V

Taste the rainbow?

Write down five descriptive words for this photograph:

What is diffraction? When waves bend around objects
Light waves don't bend around a barrier, but sound waves do.  Wave Applet

AM radios have a long wavelength AM radio waves can diffract around large building and mountains, reception is often better with AM. FM has superior sound quality but a shorter range.

Interference - waves overlap, forming a new wave
Constructive = waves add together, if these are sound waves, the sound becomes louder This is called  AMPLIFICATION

Interference - waves overlap, forming a new wave
Destructive = one wave counters the other, decreasing loudness *these waves are said to be OUT OF PHASE Watch what happens when a bridge is subject to constructive interference from wind: Tacoma Narrows

Standing Waves - waves are traveling in opposite directions with the same  wavelength and amplitude
This is difficult to visualize, so lets watch the video of a standing wave being formed in a tank. How would you describe this wave? Many instruments rely on standing waves for sound Ex. Violin, Drum, Flutes  Standing waves don't seem to go anywhere....  Surfing a standing wave

Check out how tuning forks have their own frequencies.
RESONANCE  All objects have their own natural frequencies of vibration, which depend on size, materials and shapes.  Every bell sounds different Resonance refers to the vibration of an object as it absorbs energy at its natural frequency Check out how tuning forks have their own frequencies. Bridge Resonance

How can the bending of light be used to create invisibility?

Rhymes With Wave 1. If you give blood, you might _____________ a life.
2.  If you text and drive, you might enter an early __________. 3.  Soldiers who fight wars are very _____________. 4.  A bat lives in a _________________ 5.  A sidewalk has been __________ (d) 6.  My friend ______________ me a present. 7.  Sometimes, I _____________ white castle hamburgers.

QUIZ  TIME Quiz Name:         Waves II (only covers last half of notes)

Match the term to its description.
1.  When waves overlap and either increase or decrease the effect. 2.  When a wave bounces off an object and returns 3. When a wave bends as it travels around an object 4.  When light bends as it changes medium (like going from air to water) A.  refraction B.  diffraction C.  interference D.  reflection

5. All objects vibrate at a certain frequency, like a tuning fork
5.  All objects vibrate at a certain frequency, like a tuning fork.  This is called ______________________ 6.  Which type of radio would give you better reception if you were traveling in the mountains? 7.  If two waves combine to make a bigger wave, it is called  ______________________. 8.  When you pass light through a water molecule, it separates and creates a __________________ 9.  The water molecule serves as a  ___________ 10.  What color comes after orange on the rainbow?            ___________________________