20.3 Wave Interference and Energy
Date, Section, Pages, etc.
Mr. Richter
Agenda
Warm Up
Collect Labs
Review HW
Introduction to Interference
Notes:
The Superposition Principle
Waves and Energy
Objectives: We Will Be Able To…
Describe the superposition principle with constructive and
destructive interference.
Explain which properties affect wave energy and why.
Warm-Up:
Can two waves be in the same place at the same time?
If yes, what do you think happens there?
If not, why not?
The Superposition Principle
The Superposition Principle
Waves are not physical things.
They are energy.
This means the more than one
wave can exist in the same
place at the same time.
Think about sound: can you
hear more than one thing at
once?
Of course!
The Superposition Principle
When waves collide, their vibrations combine.
The superposition principle states that the total vibration at
any point is the sum of the vibrations of each individual
wave.
The Superposition Principle:
Constructive Interference
Constructive interference
occurs when two wave pulses
combine to make a larger
amplitude.
Example: if the number of
guitars playing the same note is
doubled, the amplitude is
increased (it gets louder!)
The Superposition Principle:
Destructive Interference
Destructive interference
occurs when two wave pulses
combine to make a smaller
amplitude.
Example: noise-cancelling head
phones.
Waves and Energy
Waves and Energy
Reminder: the main idea about waves –
Waves transfer energy from place to place without
transferring matter.
There are two factors that affect the energy of a wave:
frequency – how often the energy arrives
amplitude – how much energy arrives each time
Waves and Energy: Frequency
The greater the frequency
of a wave, the more energy
it carries.
Wave energy is
proportional to frequency.
Example: trying to whip a
rope more often.
Waves and Energy: Amplitude
The greater the amplitude
of a wave, the more energy
it carries.
Wave energy is
proportional to amplitude.
Example: turning up the
volume.
Wrap-Up: Did we meet our objectives?
Describe the superposition principle with constructive and
destructive interference.
Explain which properties affect wave energy and why.
Homework
p. 447 #1, 2, 4, 5
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