th Grade: Sound and Light (Module J) - Epiphany Catholic School · 2020-01-09 · Unit 1•As a...

6th Grade: Sound and Light (Module J)

Unit 1: Introduction to Waves

Lesson 1: Waves

Lesson 2: Properties of Waves

Copyright © Houghton Mifflin Harcourt Publishing Company

• Waves: disturbances that transfer energy from one place to another.

• Some waves, such as ocean waves, transfer energy through a medium(material wave travels through)

• Some waves, such as light waves, can transfer energy without a medium

Ex: water

Unit 1 Lesson 1 WavesWhat are waves?

sound waves

•Highest point – crest• Lowest point – trough

• Draw one and label it!• Do #7 and #8 on page 7


Unit 1 Lesson 1 Waves


1. Longitudinal wave – particles vibrate in the SAME DIRECTION (parallel) as the wave travels

Ex. Sound waves

-Compressions - when the coils (or particles) are close together

-Rarefactions - when the coils are far apart.

Unit 1 Lesson 1 WavesWaves transfer energy in different ways


2. Transverse wave – particles move perpendicular

to the direction the wave travels

ex. Water waves

-Wave moves up and down




• Earthquakes send out both types of waves.

• Primary waves (P waves) are longitudinal waves. They always arrive first.

• Secondary waves (S waves) are transverse waves. They always arrive second.

• They can combine to form a surface wave, like ripples on a pond.

• Do 10, 11, 12 & 13 on p. 8 & 9


• Mechanical waves - Waves that require a medium (like water waves)

• Can be longitudinal or transverse

• Some can travel through more than one medium

• ex: sound waves can move through air, water,and a solid wall.

• Mechanical waves can’t travel without a medium.

Unit 1 Lesson 1 WavesTypes of Waves

• Electromagnetic wave - a disturbance in electric and magnetic fields

• Also called EM waves

• All are transverse waves

• Ex: Sunlight (visible light and UV light), radio waves, microwaves, and X-rays.

• In empty space, all EM waves travel at the same speed – the speed of light.


Unit 1 Lesson 1 WavesTypes of Waves, con’t

• Do page 11

The size of the wavelength determines the wave

(the next lesson!)

Lesson 2: Properties of Waves

Describing waves

Amplitude - measure of how far the particles in the medium move away from their normal rest position

Wavelength - distance from any point on a wave to an identical point on the next wave

-ex. From crest to crest, or trough to trough

- Length of one cycle, or repetition

• Read and do page 18


Unit 1 Lesson 2 Properties of Waves

• What is the wavelength of this wave? What is the wave’s amplitude?

• Wave period - time required for one wavelength to pass a given point

• Frequency - how many cycles occur in an amount of time, (usually 1 second)• Measured in hertz (Hz) – one cycle per second


Describing waves, con’t.

• Read, analyze and do page 19

• Period and frequency are the INVERSE of each other


• Some waves carry more energy than others.

• mechanical wave:greater amplitude = more energy

• electromagnetic (EM) waves:greater frequency = more energy

Unit 1 Lesson 2 Properties of WavesHow much energy can a wave carry?

•Read p

age 2

0


Unit 1 Lesson 2 Properties of Waves• As a wave travels through a medium, energy gets lost to the medium

• Higher-frequency waves lose energy more readily than lower-frequency waves lose energy.• Ex: when you stand far from a concert, you

might hear only the low-frequency (bass) sounds.



• Read & do page 21

• Many waves spread out in circles or spheres, called wavefronts.

• As the circle expands, there is less energy available on the wavefront.


• Wave speed, or the speed at which waves travel, depends on the properties of the medium.

• Waves travel faster in liquids than gas and faster in solids than liquids

• BUT more slowly in a denser medium OF THE SAME STATE OF MATTER.

Unit 1 Lesson 2 Properties of WavesWhat determines the speed of a wave?

Tracking earthquake waves

Q: Would a wave travel faster in air or water?A: Water

Q: would a wave travel faster through a table or through water?A: a table

Q: would a wave travel faster through a more dense solid (like metal) or a less dense solid (like wood)?A: A less dense solid (wood)

Q: Would a wave travel faster through a more dense liquid like oil, or a less dense liquid like water?A: a less dense liquid like water


• In gases, wave speed is higher at higher temperatures.

• All electromagnetic waves travel at the same speed in empty space, • Travel more slowly through a denser

medium• Ex: air to water

Unit 1 Lesson 2 Properties of WavesSpeed of a wave, con’t

• Speed is distance divided by time.


Unit 1 Lesson 2 Properties of WavesHow to we CALCULATE speed?

• So… Wave speed = wavelengthwave period

• For a wave, distance = wavelength• Time = wave period

• Remember that frequency and wave period are inverses of each other, so we can rewrite it like this:

• Wave speed = frequency x wavelength

Or

• Wavelength = wave speedfrequency

• Read & do page 23

How can we describe a wave?



• What is the wavelength of this wave? What is the wave’s amplitude? – Draw this in your notes!

th Grade: Sound and Light (Module J) - Epiphany Catholic School · 2020-01-09 · Unit 1•As a...

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