Unit 3 Session 21 Introduction to Waves

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?

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.

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

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

Table of Contents Unit 3 Waves Waves Overview Session 20 P. 1 Introduction to Waves Session 21

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.

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.

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.

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**

Another View

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

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

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

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.

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

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

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