1. Unit 3 Session 21 Introduction to Waves

2. Warm Up:
When an earthquake occurs, it produces waves that are recorded at all points over the world by instruments called seismographs. By comparing the data that they collected from these seismographs, scientists discovered that the interior of the earth must be made up of layers of different materials. How did they conclude this?

3. Warm Up Answer:
The data from the seismographs showed that waves traveled at different speeds as they passed through different parts of the earth’s interior. Waves behave differently as they travel through different types of matter.

4. Homework: Read DE Article: Getting to Know: Types of Waves
Answer the following question “ How are earthquakes and sound waves similar?”
Cloze this

5. Interactive Notebook: Title Page
Spend a minute to add a Title Page for:
Unit 3 Waves
Quarter 2
Your Name
Mrs. Baugh D8

6. Table of Contents Unit 3 Waves Waves Overview Session 20
P Introduction to Waves Session 21

7. Stadium Wave: (Model) Waves transport energy without transporting matter—Energy is transported, but the people do not move their location.
Ripples on surface of water: Individual water molecules transport the energy by colliding with the molecules around them.

8. What is sound?* A medium is matter that a wave moves through.
Sound is a form of energy that begins with a vibration.
Sounds travel in waves through a medium.
A medium is matter that a wave moves through.

9. What is a wave?* Energy is transferred through a wave. Matter is not.
Waves are moving energy
Waves are created when a force creates a vibration.
Mechanical waves- travel through a medium
Electromagnetic waves- do not need a medium to travel
Can you think of examples of each?
Which one does this picture represent?
Sound waves are mechanical because they need a medium to travel.

10. Mechanical Waves* Transverse Waves Longitudinal Waves
The motion of the medium is perpendicular to the motion of the wave
Up and Down Waves
**Light Waves**
Longitudinal Waves
The motion of the medium is parallel to the motion of the wave
Back and Forth Waves
**Sound Waves**

11. Another View

12. Longitudinal Waves* Compression When waves are close together
Rarefaction
When waves are far apart

13. Transverse Waves* Crest- highest point on a wave
Amplitude- Volume of a wave (height of a wave)
As wave height increases, volume increases
Measured in Decibels
Trough- lowest point on a wave
Frequency- Pitch, high or low (length of a wave)
As wavelength increases, pitch decreases
Measured in Hertz

14. Amplitude versus Frequency
Which one will have the higher volume?
Frequency
Which one will have the higher pitch?

15. What can you hear? Decibels (dB): Volume Hertz (Hz): Pitch
Normal Speech: 60dB
Library: 40dB
Close Whisper: 20dB
Jet Engine: 140dB
Loud Rock Music: 110dB
Subway Train: 100dB
Busy Street Traffic: 70dB
120dB or above usually causes pain to the ear
Hertz (Hz): Pitch
Young people can hear frequencies between 20-20,000 Hz
Dogs can hear frequencies that range from 67-45,000 Hz
As you age, your ability to hear high frequency sound decreases.

16. Now you will create a diagram for the parts of a wave.
Use string and tape.
An example is on the next slide.

17. Diagram of a Transverse Wave*
CREST
AMPLITUDE
Copy this out and shrink for Cloze
TROUGH
WAVELENGTH

18. Exit Ticket
Can you hear sound in outer space? Why or Why Not?