Chapter: Waves, Sound, and Light

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# Chapter: Waves, Sound, and Light - PowerPoint PPT Presentation

Table of Contents. Chapter: Waves, Sound, and Light. Section 1: Waves. Section 2: Sound Waves. Section 3: Light. Waves. 1. Waves Carry Energy, NOT Matter. A wave is a disturbance or vibration that moves through matter or space. Waves carry energy from one place to another.

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Chapter: Waves, Sound, and Light

Section 1: Waves

Section 2: Sound Waves

Section 3: Light

Waves

1

Waves Carry Energy, NOT Matter

• A wave is a disturbance or vibration that moves through matter or space.
• Waves carry energy from one place to another.
• When waves travel matter is not carried along with the waves.

Waves

1

Waves Carry Energy, NOT Matter

• A wave is a disturbance or vibration that moves through matter or space.
• Waves carry energy from one place to another.
• When waves travel matter is not carried along with the waves.

Waves

Transverse Waves

• Transverse or light waves can travel through matter or space.

Waves

Transverse Waves

• A transverse wave causes particles to move back and forth or at right angles (90).
• High points in the wave are called crests.
• Low points are called troughs.

Waves

1

Amplitude of a Transverse Wave

• The amplitude is half the distance between a crest and trough.
• As the distance between crests and troughs increases, the amplitude increases.

Waves

1

Longitudinal Waves

• Sound waves or longitudinal waves can travel only through matter.

Waves

1

Sound waves

• Longitudinal or compressional waves are also known as sound waves.
• A compressional wave causes particles in matter to move back and forth along the same direction in which the wave travels, like a pulse.

Waves

1

Sound Waves

• The places where the coils are squeezed together are called compressions
• The places where the coils are spread apart are called rarefactions.
• A series of compressions and rarefactions, at least two of each, forms a compressional wavelength.

Waves

1

Wavelength

• The wavelength of a transverse wave is the distance between two crests or two troughs.

Waves

1

Wavelength

• The wavelength in a sound (compressional) wave is the distance between two compressions or rarefactions.

Waves

Amplitude of a

Compressional Wave

• The amplitude of a compressional wave depends on the density of material in compressions and rarefactions.

Waves

1

Amplitude and Energy

• The more energy a wave carries, the larger its amplitude.
• As wave height increases, volume increases

### Transverse Waves*

Frequency- Pitch, high or low (Number of waves)

long wavelength, lower pitch

Measured in Hertz

*

### Amplitude vs Frequency

Amplitude (Volume)

Which Has the higher volume?

Frequency

Which Has the higher pitch?

Section Check

1

Question 1

Waves carry _______, not _______.

Section Check

1

Question 1

Waves carry _______, not _______.

Waves carry energy, not matter. Think of what happens when you shake one end of a rope; a wave travels along the rope, but the rope itself doesn’t move forward.

Section Check

1

Question 1

What is shown at point A, B, C and D in this illustration?

Section Check

1

A. crest

B. amplitude

C. direction wave moves

D. trough

Section Check

1

Question 3

The number of wavelengths that pass by each second is the wave’s _______.

A. diffraction

B. frequency

C. rarefaction

D. wavelength

Section Check

1

The answer is B. If you were watching a transverse wave on a rope, the frequency of the wave would be the number of crests or troughs that pass you each second.

Sound Waves

• Every sound you hear is caused by something vibrating.

For example, when you talk, tissues in your throat vibrate in different ways to form sounds.

2

Making Sound Waves

• Vibrations transfer energy to air particles, producing sound waves in air.

Sound Waves MUST travel through matter. it needs the vibration of molecules to MOVE. The more molecules the faster Sound Can Move. Which State of Matter Has the MOST molecules?

### Since Sound Waves MUST travel through matter. Is there Sound in Space? Remember, outer space is a vacuum w/ no matter.

Sound Waves

The Speed of Sound

• The speed of sound depends on the matter through which it travels.
• Sound waves travel faster through solids because the particles are closer together. Then liquids and last gases.

http://www.turtlediary.com/kids-science-experiments/sound-waves-experiment.html

Sound Waves

Sound Waves are Compressional Waves

• Since sound waves can only travel through matter, the energy carried by a sound wave is transferred by collisions between particles.

http://www.turtlediary.com/kids-science-experiments/sound-waves-experiment.html

Let’s see this in action!

Sound Waves

2

The Loudness of Sound

• What makes a sound loud or soft?
• The difference is the amount of energy.
• Loud sounds have more energy than soft sounds.

What can we do with this energy? How can we harness it?

Sound Waves

Pitch

• Pitch is what we think of when we hear a wave’s frequency.
• Sounds with low frequencies have low pitch
• Sounds with high frequencies have high pitch.

Sound Waves

Hearing and the Ear

• The ear is a complex organ that can detect a wide range of sounds.
• The ear can be divided into three parts—the outer ear, the middle ear, and the inner ear.

Sound Waves

Hearing and the Ear

• The three parts—
• The outer ear
• Acts like a funnel for sound waves
• The middle ear
• Increases the size of the vibrations
• (Ear Drum)
• The inner ear
• Changes the vibrations to nerve signals

http://science.howstuffworks.com/29843-understanding-sound-waves-video.htm

Sound Waves

2

Hearing and the Ear

http://www.childrensuniversity.manchester.ac.uk/interactives/science/brainandsenses/ear/

Section Check

2

Question 1

Every sound you hear is caused by something that is _______.

A. compressing

B. loud

C. moving

D. vibrating

Section Check

2

The answer is D. The sound of your voice is caused by vibrations in your vocal chords.

Section Check

2

Question 2

Sound waves travel faster through _______ than they do through water.

A. gases

B. liquids

C. plasma

D. solids

Section Check

2

The answer is D. This table shows that sound waves travel faster through solids than they travel through water.

Light Waves

3

Waves

1

Waves Can Change Direction

• Waves don’t always travel in a straight line.
• Waves can change direction when they travel from one material to another.
• Waves can:
• reflect (bounce off a surface)
• refract (change direction)
• or diffract (bend around an obstacle).

Light Waves

3

Reflection

• When a light wave bounces of a surface and the wave is reflected.

Light Waves

3

Refraction

• When a light wave moves from air to water, it slows down.
• This change in speed causes the light wave to bend.
• Refraction is the change in direction of a wave

Light Waves

3

Diffraction

• Waves can change direction by diffraction, the bending of waves around an object.
• The amount diffraction or bending of the wave depends on the size of the obstacle the wave encounters.
• If the size of the obstacle is much larger than the wavelength, very little diffraction occurs.

http://www.acoustics.salford.ac.uk/feschools/waves/diffract.php

Light Waves

1

Electromagnetic Waves

• Light, radio, and X rays are examples of electromagnetic waves.
• Electromagnetic waves are transverse waves.
• They contain electric and magnetic parts that vibrate up and down perpendicular to the direction the wave travels.

Light

3

Waves in Empty Space

• Electromagnetic wavesare waves that can travel through matter or through empty space.

Light

3

The Speed of Light

• When light travels in matter, it interacts with the atoms and molecules in the material and slows down.
• As a result, light travels fastest in empty space, and travels slowest in solids.

Light

3

The Electromagnetic Spectrum

• The electromagnetic spectrum is the complete range of electromagnetic wave frequencies and wavelengths.

Light

3

The Electromagnetic Spectrum

• At one end of the spectrum the waves have low frequency, long wavelength, and low energy.

Light

3

The Electromagnetic Spectrum

• At the other end of the spectrum the waves have high frequency, short wavelength, and high energy.

Light

3

The Electromagnetic Spectrum

• Visible light is the part of the electromagnetic spectrum that can be seen with the eye

Light

The Electromagnetic Spectrum

3

• Different colors of light have different wavelengths

Light

3

The Eye of Seeing Light

• You see an object when light is emitted or reflected enters your eye.

Light

3

The Eye of Seeing Light

• The cornea and the lens focus light waves that enter your eye so that a sharp image is formed on the retina.
• Special cells in the retina cause signals to be sent to the brain when they are struck by light.

http://www.childrensuniversity.manchester.ac.uk/interactives/science/brainandsenses/eye/

Light

The Eye of Seeing Light

Newton’s Color Wheel

3

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/newton/

Section Check

3

Question 1

Unlike longitudinal waves, electromagnetic waves can travel through _______.

Section Check

3

Question 1

Unlike longitudinal waves, electromagnetic waves can travel through _______.

Electromagnetic waves can travel through empty space.

Section Check

3

Question 2

No material thing, including spaceships, can move faster than _______.

Section Check

3

Question 2

No material thing, including spaceships, can move faster than _______.

The answer is the speed of light. Light speed is the upper limit on travel through space.

Section Check

3

Question 3

Which contains a higher frequency?

A. gamma rays B. infrared waves C. Microwaves D. radio waves

Section Check

3