20.3 wave interference and energy

20.3 Wave Interference and EnergyDate, 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