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Properties �of Waves

Presented by Kesler Science

Vers. 07/2020 © Kesler Science, LLC

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Essential Questions:

Reflect on the Essential Questions before you dive in…

1. If you were quizzed today, which questions would you know the answers to already?

2. Which questions would you need to learn more about to answer confidently?

How do matter and energy interact when waves are generated?
What are the two main types of mechanical waves?
What are properties of waves?

Properties of Waves

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Waves

A disturbance that transfers energy from place to place
Remember that energy is the ability to do work
Example: The energy carried by a wave can lift a large ship.

What is the definition of energy?

Properties of Waves

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What Causes Waves

Waves are generated when a source of energy forces the matter in a medium (solid, liquid or gas) to vibrate.

Vibration – A repeated back-and-forth or up-and-down motion.

What is the energy source in each picture?

Properties of Waves

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Mechanical Waves

Mechanical waves �only travel through �a medium

Examples:

Ocean waves travel through water (liquid)
Sound waves travel through air (gas)
A wave can travel along a rope (solid)

Properties of Waves

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Electromagnetic Waves

Some waves can travel through empty space �such as:

X-rays
Visible light
Microwaves
Radio
UV - ultra violet

What type of waves have the highest energy?

Properties of Waves

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Two Types of Mechanical Waves

Waves are classified according to how they travel through a medium

Transverse Waves (A)
Longitudinal Waves (B)

A

B

What are the two types of mechanical waves?

Properties of Waves

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Transverse Waves

Waves that move through the medium at right angles to the direction the waves are traveling.

Transverse means “across”

As a transverse wave moves in one direction, the particles of the medium move perpendicular to the direction of the wave, or across it.

Direction of wave

Direction of medium

Right Angle

What does perpendicular mean?

Properties of Waves

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Transverse Wave Vocabulary

Crest – where the displacement of the medium is at a maximum�
Trough – where the displacement of the medium is at a minimum�
Rest position – where the medium shows no disturbance.

Trough

Rest Position

Crest

Properties of Waves

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Amplitude

The vertical distance between a peak or a valley and the resting position in a transverse wave.

Amplitude

Properties of Waves

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Properties (cont.)

Wavelength

The distance between two corresponding parts of a wave

Crest to crest or trough to trough (transverse wave)

Wavelength

Properties of Waves

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Longitudinal Waves

The medium moves parallel to the direction the waves �are traveling

The medium moves back-and- forth in the same direction as the wave travels

Direction of medium

Direction of wave

What two things are moving parallel to each other?

Properties of Waves

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Longitudinal Wave Vocabulary

Compression – Particles are close together.

Rarefaction – Particles are spread out.

Direction of medium

Compression

Rarefaction

Direction of wave

Properties of Waves

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Amplitude

A measure of how compressed or rarefied the medium becomes in a longitudinal wave.

Amplitude

Properties of Waves

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Describe the particle motion of a longitudinal wave. Which type of medium (state of matter) do you think would best carry them?

Think About It

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Properties (cont.)

Wavelength

The distance between two corresponding parts of a wave

Distance from one compression to the next (longitudinal wave)

Wavelength

Properties of Waves

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Properties (cont.)

Frequency

The number of complete waves (wavelengths) that pass a given point in a certain amount of time

Number of vibrations per second
Measured in units called hertz (Hz)

1 vibration per second = 1 Hz

What unit is frequency measured in?

Properties of Waves

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Use your knowledge of waves and the graph shown to determine the frequency of Wave C. What does it tell you about the speed of the wave?

Think About It

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Properties (cont.)

Speed

How far the wave travels in a unit of time, or distance divided by time

The speed, wavelength, and frequency of a wave are related to each other by mathematical formulas.

Unit for speed is meters per second, or m/s

Speed = Wavelength x Frequency

or

Frequency = Speed / Wavelength

or

Wavelength = Speed/ Frequency

S

W

F

Properties of Waves

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A wave on a lake has a wavelength of 0.5 m and a frequency of 2 Hz (2 Hz = 2 per second, or 2/s).

To find the speed of the wave, use this formula:

Speed = Wavelength x Frequency

Speed = 0.5 m x 2 Hz

= 0.5 m x 2/s

= 1 m/s

Speed Problem

Properties of Waves

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Explain why foam is a good material choice for exercise, yoga, stunt, and gymnastics mats.

Think About It

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Give your best answer to...�

Describe how matter and energy interact when waves are generated

Distinguish between the two main types of mechanical waves

Identify the properties of waves

Check for Understanding

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Still have questions?

Which essential questions do you still need help to understand?