Introduction to Properties of Waves

Introduction to Properties of Waves

Middle School

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Learning Objectives

Key Vocabulary

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Wave

A repeating pattern of disturbance that transfers energy from one place to another without transporting matter.

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Mechanical Wave

A wave, such as a sound wave, that must travel through a medium to transfer its energy.

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Transverse Wave

A wave where particles of the medium vibrate perpendicularly to the direction the wave's energy is traveling.

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Longitudinal Wave

A wave where particles of the medium vibrate parallel to the direction the wave's energy is traveling.

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Amplitude

The maximum distance a particle in a wave moves from its equilibrium position, indicating the wave's energy.

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Wavelength

Key Vocabulary

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Frequency (f)

Frequency is how many complete wave cycles pass a certain point in a given amount of time.

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Crest

The crest is the highest point or peak a wave reaches above its central resting position.

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Trough

The trough is the lowest point or valley a wave reaches below its central resting position.

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Period (T)

The period is the total amount of time it takes a wave to complete one full cycle.

What is a Wave?

• A wave is a disturbance that moves energy from place to place.

• Waves transfer energy over a distance, but not matter.

• Mechanical waves need a medium like air or water to travel.

Multiple Choice

What is the definition of a wave?

• A disturbance that moves energy from place to place.

• A substance that moves matter through a medium.

• A force that creates new matter and energy.

• A particle that stays in one location.

Multiple Choice

What is the relationship between a wave and the matter it travels through?

• The wave carries the matter with it as it travels.

• The wave converts the matter into pure energy.

• The wave transfers energy but does not move the matter over a long distance.

• The matter is destroyed as the wave passes through it.

Multiple Choice

If a large explosion happens on a distant star, why would astronauts in a nearby spaceship see the light but not hear the sound?

• Sound is a mechanical wave and cannot travel without a medium like air.

• The energy from the explosion is not strong enough to reach the spaceship.

• The light from the explosion travels faster than the sound.

• The spaceship's hull blocks all forms of energy from entering.

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Types of Mechanical Waves

Transverse Waves

• ​Particles of the medium move perpendicular to the direction of the wave's energy.

• ​​Imagine flicking a rope up and down to create a wave that travels horizontally.

• ​Examples of these waves include seismic S waves and waves created on a string.

Longitudinal Waves

• ​Particles of the medium move parallel to the direction of the wave's energy.

• ​​Think of pushing a Slinky forward and backward to see the compression travel.

• ​Examples of these types of waves include sound waves and seismic P waves.

Multiple Choice

What is the key difference used to classify mechanical waves as either transverse or longitudinal?

• The direction the particles of the medium move relative to the direction of the wave's energy.

• The speed at which the wave travels through the medium.

• The type of medium the wave is traveling through.

• The size of the particles in the medium.

Multiple Choice

Which statement accurately compares the two types of mechanical waves described?

• A transverse wave has examples like sound waves, while a longitudinal wave has examples like seismic S waves.

• In a transverse wave, particles move perpendicular to the wave's energy, while in a longitudinal wave, they move parallel to it.

• A transverse wave can be created with a Slinky, while a longitudinal wave can be created with a rope.

• In a transverse wave, particles move back and forth, while in a longitudinal wave, they move up and down.

Multiple Choice

If you drop a pebble into a pond, it creates ripples that move outward. Toy ducks floating on the water bob up and down as the ripples pass. Based on this observation, how would you classify this wave and why?

• A transverse wave, because the toy ducks move perpendicular to the direction of the wave's energy.

• A longitudinal wave, because the toy ducks move parallel to the direction of the wave's energy.

• A transverse wave, because water waves are a type of seismic S wave.

• A longitudinal wave, because the wave is compressing the water like a sound wave.

Measuring Waves: Amplitude, Wavelength, and Frequency

• ​Amplitude is a wave's height from the midline, affecting its energy and loudness.

• Wavelength is the distance from one wave crest to the next.

• Frequency is the number of waves that pass a point in a certain time.

Multiple Choice

What is the term for the distance from one wave crest to the next?

• Amplitude

• Wavelength

• Frequency

• Energy

Multiple Choice

What is the relationship between a wave's amplitude and its energy?

• A wave with a larger amplitude carries more energy.

• A wave with a smaller amplitude carries more energy.

• A wave's amplitude and energy are not related.

• A wave's energy depends only on its frequency.

Multiple Choice

If two waves are traveling at the same speed, but Wave X has a shorter wavelength than Wave Y, what can you conclude?

• Wave X has a higher frequency.

• Wave X has a lower frequency.

• Wave X has the same frequency.

• Wave X has a larger amplitude.

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Wave Relationships and Equations

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Multiple Choice

What three properties of a wave are related by the wave equation?

• velocity, wavelength, and frequency

• amplitude, energy, and period

• frequency, amplitude, and energy

• period, velocity, and energy

Multiple Choice

What happens to a waves energy if its frequency increases?

• The energy increases.

• The energy decreases.

• The energy stays the same.

• The energy becomes zero.

Multiple Choice

If a wave's amplitude is doubled and its period is cut in half, what is the most likely effect on the wave's energy?

• The energy will significantly increase.

• The energy will significantly decrease.

• The energy will stay the same.

• The energy will be cut in half.

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Common Misconceptions

Misconception	Correction
Waves carry matter with them.	Waves transfer energy, but particles of the medium only oscillate.
Changing a wave's amplitude also changes its frequency or pitch.	Amplitude and frequency are independent properties of a wave.
Louder sounds have a higher pitch.	Loudness is determined by amplitude, while pitch is determined by frequency.

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Summary

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

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• 3

• 4