Unit 4, Chapter 12

Integrated Science

Unit Four: Sound and Waves

12.1 Waves

12.2 Waves in Motion

12.3 Natural Frequency and Resonance

Chapter 12 Waves

Chapter 12 Learning Goals Learn the role waves play in our daily lives, including

our effort to communicate.

Learn the parts and shapes of waves.

Model transverse and longitudinal waves and their characteristics with a stretched string.

Explore the properties of waves (like reflection and diffraction) with water.

Investigate resonance and harmony using an electronic synthesizer.

Learn how natural frequency and resonance are involved in making music.

Chapter 12 Vocabulary Terms circular waves continuous harmonics constructive interference crest hertz destructive interference diffraction fundamental plane longitudinal wave natural frequency

reflection refraction resonance response transverse wave trough standing wave wave fronts waves

12.1 Waves

Key Question:

How do we make and describe waves?

*Read text section 12.1

AFTER Investigation 12.1

12.1 Waves If we poke a ball floating on

water, it will bob up and down (harmonic motion).

The oscillating ball creates a wave on the water surface.

The first ball can make a second ball that is farther away oscillate.

Explain the transfer of energy.

12.1 Why study about waves?

useful puzzling

12.1 Evidence of waves Anytime you see a vibration that moves Anything that makes or responds to sound Anything that makes or responds to light Anything that transmits information through the air (or space) without wires

— cell phones, radio, and television. Anything that allows you to “see through” objects

— ultrasound, CAT scans, MRI scans, and X rays

12.1 Transverse and Longitudinal WavesA transverse wave has its oscillations

perpendicular to the direction the wave moves.

A longitudinal wave has oscillations in the same direction as the wave moves.

12.1 Frequency, Amplitude and

Wavelength

12.1 Wavelength

12.1 Speed

v = f

frequency (cycles/sec)

wavelength (m)

speed (m/sec)

12.2 Graphs of Harmonic MotionKey Question:

How do waves move and interact with things?

*Read text section 12.2 AFTER Investigation 12.2

12.2 Waves in Motion Waves have crests and troughs.

The crest of a wave is sometimes called a wave front.

The shape of a wave is determined by its wave front.

12.3 Natural Frequency and Resonance

Key Question:

What is resonance and why is it important?

*Read text section 12.3

AFTER Investigation 12.3

12.3 Natural Frequency and Resonance

1. All things in the universe have a natural frequency, and many things have more than one.

2. If you know an object’s natural frequency, you know how it will vibrate.

3. If you know how an object vibrates, you know what kinds of waves it will create.

4. If you want to make specific kinds of waves, you need to create objects with natural frequencies that match the waves you want.

12.3 An example of resonance

12.3 Standing Waves and Harmonics