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Unit 4:  Waves, Sound, and Color Unit 4:  Waves, Sound, and Color

Unit 4: Waves, Sound, and Color - PowerPoint Presentation

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Unit 4: Waves, Sound, and Color - PPT Presentation

vibrations repetitive back and forth motions Waves a traveling disturbance that carries energy from one location to another Think about waves like ripples in a pond Mechanical Waves ID: 736504

wave waves sound color waves wave color sound max light change position direction air colors spring cones rest wavelength

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Slide1

Unit 4: Waves, Sound, and ColorSlide2

vibrations

- repetitive back and forth motions

Waves – a traveling

disturbance that carries energy from one location to another. Think about waves like ripples in a pond. Slide3

Mechanical Waves

Mechanical

waves – must travel through

matter.Matter = solids, liquids, and gases.CANNOT travel through a vacuum. Slide4

Electromagnetic Waves

Electromagnetic

waves – can travel through transparent material and vacuums.

Example? Light.Slide5

Longitudinal Waves

: compression waves

Transverse Waves

: sinusoidal wavesSlide6

Wave Terms!

Wavelength

(

λ) - the distance between two identical points on two consecutive waves.Frequency (f

) –

The number of oscillations, vibrations, or waves passing a reference point per second. We measure this in

hertz

(Hz).

Period

(T) – The time for one single oscillation, vibration, or wave.Wave Speed (c) – How fast a wave travels. Slide7

Note: Frequency and wavelength are inversely proportional to each other.

Greater frequency

 shorter wavelength

Lower frequency  greater wavelengthSlide8

Mechanical Waves

Energy begins moving via

disturbance

or vibration through an elastic source. Physical medium is needed.Energy transfers away

from the source.

It temporarily

changes

the medium.

Medium

goes back to the way it was after the wave has passed.The height of wave (amplitude) weakens the further it gets from the disturbance.Slide9

Stretch the spring using WORK against resistance, Create PE. If released, the spring will “snap back” to restore its original shape

Rest (equilibrium position): No motion, the shape of the spring is maintained by its restoring force.

Compress the spring using WORK against resistance, Create PE. If released, the spring will “snap back” to restore its original shape.

Energy relationship of a springSlide10

Stretch the spring to induce PE, then release!

Compressed position: v = 0, PE = 100%. Instantaneous change in direction.

Passing through the rest position (equilibrium position): v = max, PE = 0

Passing through the rest position (equilibrium position): v = max, PE = 0

Passing through the rest position (equilibrium position): v = max, PE = 0

Stretched position: v = 0, PE = 100%. Instantaneous change in direction

Simple harmonic motion of a springSlide11

Rest position

v = max, PE = 0

Max h: v = 0, PE = max

Instantaneous change in direction

Simple harmonic motion of a pendulum

Max h: v = 0, PE = max

Instantaneous change in directionSlide12

Simple harmonic motion of a standing wave (e.g., plucked string)

Rest position: v = max, PE = 0

Max displacement: v = 0, PE = max

Max displacement: v = 0, PE = maxSlide13

Air molecules become compressed at the condensations (increased pressure) and become diffused at the rarefactions (decreased pressure).Slide14

Human hearing range:

20-20,000

hertz

Sound travels fastest through solids and slowest through gases.Slide15

Why we care about waves for sound

amplitude

- the maximum displacement of the wave (or height of it).

Why we care: amplitude is the volumn of the sound. Rest - places where the wave has stopped and is sitting at equilibrium.

Why we care:

Pause

or

stop

in the music. Pause between notes.

Compressions = louderRarefactions = softer or quieter.Slide16

Reflection

- when a wave bounces off of something back toward you.

Why we care: This is how we

echo sound. Refraction - when a wave is bentWhy we care: this is what causes an changes.Slide17

Refraction tendencies

As sound waves pass through an air-solid boundary

Air

 Glass: Speed up and change direction

Glass  Air: Slow down and change direction

As sound waves pass through cold air-warm air boundary

Cold air

 warm air: Speed up and change direction

Warm air  cold air: Slow down and change direction

As sound waves pass through two different solids with different densities More dense

 Less dense: Slow down and change direction Less dense  More dense: Speed up and change directionSlide18

Intencity

of sound is measured in

pitch.

Anything over 80 decibels (dB) can cause permanent damage to your ears. Resonance – the vibration of sound left after the initial cause has been hit. Slide19

Beat

Beat

Beat

Beat

Noise

Noise

Noise

Noise

Wave 1

Wave 2

Wave functions are additive. Wave 1 and Wave 2 have different frequencies and wavelengths. When Wave 1 and Wave 2 interact, the sum of the waves will produce noise and beats. Noise is where individual waves are out of phase, thus produce non-harmonic multiple tones. Beat is where individual waves are in phase and the amplitudes combine to produce a harmonic pure tone.Slide20

Wavelengths and Sound

Wavelengths cause “notes.”

The

shorter the wavelength, the higher the sound. The longer the wavelength, the lower the sound. Slide21

Doppler Effect

The seeming change in

sound

because of the object’s or your movement.http://www.youtube.com/watch?v=z0EaoilzgGESound travels at the same speed but the objects or you

moves.Slide22

LIGHT

Light is

electromagnetic

waves, NOT longitudinal/compression. Slide23

Why we see

Our eyes have two main types of receptors:

rods

and cones.Rods- measure “lightness,” “darkness,” and register motion. cones- detect color. Slide24

Our cones have

3

color receptors in them. These are the three primary colors IN LIGHT.

RedBlueGreenSlide25

This is our color spectrum. We see all of this because of those 3 color cones.

Other animals have different cones, and can see other colors. Slide26
Slide27

Animal Color Trivia

Dogs only have

2

color cones, so they can see shades of green, blue, and some yellows. Nocternal hunting animals can see into the infrared light spectrum. Bees can see into the ultraviolet spectrum, and scientists call that “bee yellow.” Butterflies have 5 different color cones in their compound eyes.

The mantis shrimp has 16. Slide28

More facts about the mantis shrimp

http://

theoatmeal.com/comics/mantis_shrimp

http://www.youtube.com/watch?v=F5FEj9U-CJMSlide29

Back to light

Light

reflects

and refracts.Reflection - we see reflection/color.Refraction - Bends light. This is why we don’t see things straight on in water. Slide30

When light bends through mist, it’s bending over and over again through thousands of

water droplets.

Every time it goes through a droplet, the light

changes.This makes us see the full color spectrum.In other words: a rainbow.Slide31

We see an object’s color because that’s the only color that object is

reflecting.

All the other color it absorbs.

WHITE – ALL color wavelengths reflected. BLACK – absence of color. NOTHING is reflected, EVERYTHING is absorbed. Slide32

Color Wheels

The Primary colors of light are red, blue, and green:

The primary colors when painting are red, blue, and yellow. Slide33

For painting: Primary colors are

red, yellow, blue.

Secondary colors are what they mix together to make:

green, purple, orange.Complementary colors are colors opposite on the color wheel. When mixed they make brown.Slide34