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Understanding Waves: Properties, Types, and Interactions

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U3: What does a wave tell us?
Key Concept: Change
Related Concepts: Form, Patterns
Global Context: Orientation in Space and Time
+Constraints & adaptation
“Societies manage constraints and adapt to changes
by forming patterns.”
In this unit you will be assessed on Criterion A and D
Characteristics of Waves
Table of Contents
What Are Waves?
Properties of Waves
Interactions of Waves
What are Waves?
What are Waves? - Vocabulary
• Wave – a disturbance involving the transfer of energy from
place to place
• Energy – the ability to do work.
• Medium – The material through which a wave travels
• Mechanical Wave – waves that require a medium
• Vibration – a repeated back-and-forth or up and down motion
Mechanical waves form when a source of energy causes a
medium to vibrate.
What are Waves? - Vocabulary
• Transverse Wave – A wave that vibrates the medium at right
angles, or perpendicular, to the direction in which the wave
travels.
• Crest – A high point in a transverse wave
• Trough – A low point in a transverse wave
• Longitudinal Wave – vibrates the medium in the same
direction in which the wave travels
• Compression – An area where the coils are close together
• Rarefaction – An area where the coils are spread out
WAVES
A wave is a disturbance causing the transfer of energy from
place to place. MOST waves (not all) need a medium to travel
through.
A medium can be:
• Gas (for example ______ )
• Liquid (for example ______ )
• Solid (for example ______ )
What kind of waves DON’T need a medium?
What Are Waves?
Motion in a Transverse Wave
What are the crest, trough, and rest position?
What Are Waves?
Motion in a Longitudinal Wave
Which are the areas of compression and rarefaction in the diagram?
What Are Waves?
A Picture of a Sound Wave
The picture shows an area of air as the compressions and rarefactions
of a sound wave pass through it. The dots represent air particles.
Where are the rarefaction and the compression areas?
What Are Waves?
Waves Transfer
Energy
A wave moves
the bottle in a circular
motion. After the wave
passes, the bottle
returns to where it
started. How will the
bottle look in the
bottom picture?
Properties of Waves
Properties of Waves - Vocabulary
• Amplitude – The maximum distance the medium vibrates from
the rest position
• Wavelength – The distance between two corresponding parts
of a wave
• Frequency – The number of waves that pass a given point in
a certain amount of time
• Hertz – unit of frequency; number of waves per second
Properties of Waves
Amplitude
The amplitude of a transverse wave is the maximum distance the
medium vibrates from the rest position. What are the parts of the
wave?
http://www.youtube.com/watch?v=OGyRe_SGnck
Properties of Waves
Properties of Waves
All waves have amplitude, wavelength, frequency, and speed.
TRANSVERSE WAVE
Wavelength
Crest
Amplitude
Rest position
Trough
Wavelength
Direction of wave
LONGITUDINAL WAVE
Compression
Wavelength
Rarefaction
Properties of Waves
The table shows measurements of some properties of a sound wave in
water and in air. Complete the table.
Review Quiz
Interactions of Waves
Interactions of Waves - Vocabulary
• Reflection – When a wave hits a surface, any part of the wave
that cannot pass through the surface bounces back. This
interaction with the surface is reflection
• Refraction – The bending of waves due to the change in
speed
• Diffraction – When a wave moves around a barrier or passes
through an opening in a barrier, it bends and spreads out.
These interactions are called diffraction
• Interference – The interaction between waves that meet
Interactions of Waves - Vocabulary
• Constructive interference – Interference in which waves
combine to form a wave with a larger amplitude than any
individual wave’s amplitude
• Destructive interference - Interference in which waves
combine to form a wave with a smaller amplitude than either
original wave had.
• Standing wave – A wave that appears to stand in one place,
even though it is two waves interfering as they pass through
each other.
Interactions of Waves - Vocabulary
• Node – In a standing wave, destructive interference produces
points with zero amplitude, called nodes
• Antinode – Points of maximum amplitude on a standing wave
• Resonance – An increase in amplitude of a vibration that
occurs when external vibrations match an object’s natural
frequency
Interactions of Waves
The Law of Reflection
The law of reflection states that
the angle
of incidence equals the angle of
reflection.
Interactions of Waves
Constructive
Interference
When waves combine to
form a wave with a larger
amplitude, it is called
constructive
interference.
Interactions of Waves
Destructive
Interference
Describe the
steps of
destructive
interference.
Interactions of Waves
Standing Waves
As the frequency
of the standing
wave increases,
more nodes and
antinodes are
created. Identify
the nodes and
antinodes.
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