Do NOW

• Explain the difference between kinetic and potential energy.

• Create a KWL chart and fill in the first to columns

• Copy homework: Read unit 5 lesson 2

Shout Outs

• Shout out to the following people for scoring 100% on the test last week:

• Marcus • La’Dauris• Madalee• Trevoir• Alicia• Lance• Leoriandy• Leomardo

Lab Stations

• There are 7 stations, each about 5 minutes• Each table has a set of directions. Read the

directions and complete the activity.• Stay in your chair until told to switch.• Volume at a level 2, conversations stay on task

within group• Respect others opinions

Closing Activity

• Fill out the final column of the KWL chart.

Do Now

• List and describe 3 forms of energy you have seen/used this morning.

• Copy Homework: Draw and label a transverse wave and compressional wave

Essential Question• How do we describe a wave?

• What is the difference between a transvers wave and a compressional wave?

• Explain how frequency/amplitude relates to the energy of a wave?

Waves and Sound

Wave

Wavelength

Amplitude

Waves and Sound

Frequency

Sound wave

Reflection

• Wave is a disturbance that transfers energy from one point to another.

• Electromagnetic waves can travel through empty space and matter.– Ex. Light waves

What are waves?

• Mechanical waves must travel through a medium – a substance – in order to transfer energy– Ex. Sound waves

• A medium can be a solid, liquid or gas.• The movement of particles by a wave

is called a vibration.

What are waves? (cont.)

• Waves are classified by the type of vibration they cause in a medium. –Transverse waves – when a

transverse wave travels through a medium, matter moves up and down as the wave travels through it.

• Ex. Water waves

What are waves? (cont.)

–Compressional wave– when a compressional wave travels, matter moves back and forth as the wave travels through it.

• Similar to a spring or a slinky.• Ex. Sound waves

What are waves? (cont.)

• All waves travel and transfer energy from one point to another, with little or no displacement of the particles of the medium.

• After the wave has passed, the particles end up in about the same position they started in.

What are waves? (cont.)

• Wavelength is the distance between two waves’ crests or two waves’ troughs.

• OR The distance between two waves’ compressions or rarefactions.

How can you measure waves?

• Amplitude is the height of a wave from its trough or crest to its midpoint.

How can you measure waves?

• The wave with the larger amplitude carries more energy and makes the ball bounce higher.

How can you measure waves?

• Frequency is a measure of how many wave crests or troughs pass a given point in one unit of time. – High-frequency waves have shorter wavelengths

and transfer greater energy.

How can you measure waves? (cont.)

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

• Frequency is measured in hertz (Hz), the number of waves per second.– Ex. 5 waves in 20seconds.

5 ÷ 20 = 0.25 Hz.

How can you measure waves? (cont.)

• The distance a wave travels per second determines its speed. – Ex. A boat passes within 65m of a buoy. The

waves from the boat take 5seconds to reach the buoy.

Wave speed = 65 ÷ 5 = 13m/s• The speed of a wave depends on its

medium, not its frequency!– Ex. A high-frequency wave can travel slowly

How can you measure waves? (cont.)

Do Now

• Draw and label a wave. How can we measure a wave?

• Copy Homework: Study for unit 5 lesson 1 and 2 test tomorrow

Essential Question

• How do waves cause sound?

• How is sound reflected or absorbed?

• Why is sound important?

Waves and Sound

• Sound wave is a compressional wave produced by vibrations in matter.

• Molecules in the medium moved back and forth, pushing nearby molecules.

• Because sound waves depend on the compression of matter, they need a medium to travel through.

How does sound travel?

• In sound waves, the distance between the particles affects speed.

• Sound waves move fastest through solids, slower through liquids and slowest through gases.

How does sound travel? (cont.)

Medium Speed (in m/s)

Air 334

Freshwater 1,461

Seawater 1,490

Silver 2,610

Glass 5,000

• When you look in a mirror, light waves bounce off the mirror into your eyes and enable you to see your image.

• Sound waves also reflect off of objects. • Reflection is the bouncing of a wave off

an object, changing the direction of travel. – Ex. An echo and sonar

How does sound travel? (cont.)

• The material a sound wave strikes affects how the sound wave moves.

• Hard surfaces reflect sound waves, soft surfaces absorb sound waves. –Absorption is the transfer of

energy when a wave disappears into a surface.

• Ex. Ceiling tiles, insulation

• A material that absorbs sound waves well does not reflect sound waves.

How does sound travel? (cont.)

• The pitch or the highness or lowness of a sound, depends on the frequency of the sound waves. – High pitched sounds have a

high frequency– Low pitched sounds have a low

frequency

• Most humans can hear sound waves in the range of about 20Hz to about 20,000Hz.

What are properties of sound?

• A sound’s pitch seems to change if its source or listener is moving. – This is called the Doppler effect.

What are properties of sound? (cont)

• The difference in the loudness of a sound is called volume.

• The amount of energy, or intensity (amplitude), of the sound wave determines the volume of a sound.–The larger the amplitude, the louder

the sound.

What are properties of sound? (cont)

• The volume of a sound is measured in units called decibels (dB)– Regular speech have a volume of about 60dB.– Sounds greater than 90dB can damage people’s hearing.

What are properties of sound? (cont)

• The motion of two or more waves passing through the same medium at the same time is called interference.– Ex. Two sets of speakers playing the same song

in the same room.

What are properties of sound? (cont)

• Interference can be positive for negative. – If the crests or troughs of the waves meet, they

would combine and the combined sound would be louder – constructive interference.

– If the crest of one wave meets the trough of another wave, combined amplitude is lower than the sound made by one source alone – destructive interference.

– WHICH IS A POSITIVE AND WHICH IS NEGATIVE?

What are properties of sound? (cont)

• Sound waves pass through your ear canal to your eardrum causing your eardrum to vibrate.

• The vibrations stimulate nerve cells located deep inside the ear.

• These vibrations are then converted to nerve impulses that your brain recognizes and identifies as different sounds.

How do we hear music?

How do we hear music? (cont.)

• Music is a combination of sounds that a listener finds pleasing.

• Noise is a combination of sounds that a listener finds unpleasant.

How do we hear music? (cont.)

http://www.iknowthat.com/ScienceIllustrations/sound/science_desk.swf

A. diffractionB. interferenceC. reflectionD. refraction

Which occurs when waves that overlap combine to form a new wave?

A. the next crestB. the next troughC. the next compression D. the next rarefaction

To measure the wavelength of a transverse wave, you can measure the distance from one crest to which of these?

A. amplitude B. compression C. frequencyD. wavelength

Which refers to the number of wavelengths that pass by a point each second?

Dow Now

• Explain what a wave is. What are two types of waves and how they move?

• Copy Homework: Bring in a current events article about something science related

Unit 5 Lesson 2 Review