1. Chapter 11: Waves Section 1: What are Waves? Objectives:
Explain the relationship among waves, energy, and matter.
Describe the difference between transverse waves and compressional waves.

2. Waves From what you already know about waves…
List five examples of different types of waves you have experienced.

3. Bill Nye: http://www.gamequarium.org/cgi-bin/search/linfo.cgi?id=8445
Waves
Waves: rhythmic disturbances that can carry energy without carrying matter. A wave transfers energy from one place to another without transferring matter in the process
How can waves carry energy without carrying matter?
- Molecules of matter transfer energy in a wave by bumping into one another.

4. Mechanical Waves
Mechanical Wave: a type of wave which uses matter to travel or transfer energy. (Ex: ocean, stadium waves, jump rope, sound)
A mechanical wave travels as energy is transferred from particle to particle in the medium
A medium is a substance or material that carries the wave.
There are two types of mechanical waves: transverse and compressional (also known as longitudinal)
What are at least three types of mediums through
which waves can travel?

5. WHAT IS A WAVE? ALL WAVES HAVE: 1.) amplitude 2.) wavelength
A wave is - ANY DISTURBANCE that causes energy to travel from place to place. In other words, ALL WAVES TRANSFER ENERGY THROUGH A MEDIUM.
WAVES are created when a SOURCE OF ENERGY causes a MEDIUM to VIBRATE.
All waves, however, share certain basic characteristics:
ALL WAVES HAVE:
1.) amplitude
2.) wavelength
3.) frequency
Waves CAN BE transmitted through ALL PHASES OF MATTER (solid, liquid, gas, and plasma)

6. WAVES NEED A MEDIUM!
MEDIUM – the material through which a wave travels through
This includes ALL phases of MATTER.
TYPES OF MEDIUMS
-LAND
-WATER
-AIR
Remember: this medium will NOT move as a whole as the ENERGY is transmitted through it.

7. THE TWO TYPES OF WAVES!
LONGITUDINAL /COMPRESSIONAL TRANSVERSE__________________
1.) COMPRESSIONS – (close together) ) CREST - (highest point)
Represented by the coils of the spring that
are CROWDED TOGETHER There is a MAXIMUM DISPLACEMENT
UPWARD of the particles.
2.) RAREFACTION – (far apart) ) TROUGH – (lowest point)
are SPACED APART There is a MAXIMUM DISPLACEMENT
DOWNWARD of the particles.

8. Transverse Waves
Transverse Waves: a type of mechanical wave in which the wave energy causes the medium matter to move up and down or back and forth at right angles to the direction the wave travels (Ex: A ripple on a pond, stadium wave)
The high points of the wave are called crests and the low points are called troughs.
Electromagnetic waves are transverse. List two other examples of transverse waves .
CREST - highest point of a wave
The MOTION of the WAVE and the DIRECTION of the wave are at RIGHT ANGLES.
TROUGH - lowest point of a wave
The dashed line drawn through the center represents the equilibrium (resting position) of the string.

9. Animation Transverse and longitudinal waves: http://www. youtube
Types of Waves:
Compressional Waves
Compressional/Longitudinal Waves: a type of mechanical wave in which the medium matter moves forward and backward in the same direction the wave travels
All waves are produced by something vibrating.
Two examples of longitudinal waves:
Sound traveling through air or water, waves during an earthquake
COMPRESSIONS – part of the wave where the particles are CLOSE together. (Maximum density)
RAREFACTIONS – part of the wave where the particles are SPACED APART. (Minimum density)

10. Sound Waves Sound waves are compressional waves.
Sound waves are compressional waves.
A series of compressions and rarefactions move in all directions from the object producing sound waves.
- When the object vibrates outward/up, the molecules next to it are pushed closer together causing a compression (higher pressure and density).
- When the object vibrates inward/down, the molecules have more room and spread farther apart causing a rarefaction (lower pressure and density).
You can feel the vibrations when you hold your fingers against your throat while you hum or talk
Describe how being near a source of loud sounds, such as heavy machinery or the subwoofer of a stereo, demonstrates that waves carry energy.

11. Electromagnetic Waves
Electromagnetic Waves
Electromagnetic Waves: waves that don’t require matter to carry energy .
They are transverse waves produced by the motion of electrically charged particles.
An electromagnetic wave is a wave that is capable of transmitting its energy through a vacuum (empty space).
What are three examples
of electromagnetic waves?
Sun, light, x-rays

12. Homework
Answer the Section 1 Assessment questions (#1-5) found on page 320 in your notebook.
Mini Quiz
Mini Quiz:

13. Section 2: Wave Properties
Objectives:
Describe the relationship between the frequency and wavelength of a wave.
Explain why waves travel at different speeds.
Does it take more energy to twirl a jump rope for a short or a tall person?

14. Amplitude
Amplitude: how high a wave rises above or falls below the normal
Transverse Wave: half the distance between the crest and the trough
Compressional Wave: amplitude increases as particles in compressions move closer and those in rarefactions move farther away.
AMPLITUDE IS THE HEIGHT OF THE WAVE!
Waves with high energy have a LARGE amplitude.
Waves with low energy have a SMALL amplitude.
The amplitude is the maximum distance the medium (the material through which a wave travels) moves away from its rest position.  The higher the wave moves up-and-down as it vibrates, the larger the amplitude of the resulting waves.

15. Wavelength Wavelength- the length of one complete wave cycle.
Mini Quiz:
Wavelength
Wavelength- the length of one complete wave cycle.
Transverse Waves: distance from the top of one crest to the top of the next crest or from the bottom of one trough to the next trough
Compressional Wave: distance from the center of one compression to the center of the next compression or from the center of one rarefaction to the next rarefaction
The wavelength can be measured from any point on a wave as long as it is measured to the same point on the next wave.

16. Frequency
Earthquake Frequency:
Frequency: number of wavelengths that pass a given point in 1 second; measured in Hertz (Hz)
As the frequency of a wave increases, its wavelength decreases.
The color of light and the pitch of a sound can both be determined by either the wavelength or frequency of the wave.
Pitch: highness or lowness of a sound.

17. Wave Speed
Mechanical Waves: travel faster through mediums where the atoms are closer together (ex. sound)
Would sound travel faster through water or air?
Electromagnetic Waves: travel faster through mediums where the atoms are farther apart (ex. visible light)
Would light travel faster through water or air?
Wave Speed (S) = Wavelength(λ) x Frequency(F)  
Commonly used units:
wave speed – m/s
wavelength – m
frequency – Hertz (1 wave per second)

18. Wave Speed (S) = Wavelength(λ) x Frequency(F)
Determine the speed of a wave that has a frequency of 7 Hz and a wavelength of 9 m.
If a sound wave traveling through water has a speed of 1,470 m/s and a frequency of 2,340 Hz, what is its wavelength?

19. Homework
Answer the Section 2 Assessment questions (#1-5) found on page 325 in your notebook.

20. Section 3: Wave Behavior
Objectives:
Explain how waves can reflect from some surfaces.
Explain how waves change direction when they move from one material into another.
Describe how waves are able to bend around barriers.
Why can you see your reflection in a still pond?
Why can you see the objects around
you?
Why can you hear the kids in the music room, but not see them?
Why is trying to catch a fish in a bowl with your hands harder than you think?

21. LIGHT WAVES
Light waves can pass through many media: air, water, glass, to name a few.
Light waves do not need any medium to travel.
Sunlight, moonlight, and starlight pass through the vacuum of outer space to reach us.

22. Reflection
Reflection: when a wave strikes an object or surface and bounces off
Reflection occurs when light bounces off an opaque material.
Normal- A line that is perpendicular to the surface.
- When a surface is smooth, the wave will bounce off directly and the image will be clear. When a surface is rough, the wave will bounce in many directions and the image will be unclear.

23. LAW OF REFLECTION In this law the ANGLE OF INCIDENCE is EQUAL TO the
ANGLE OF REFLECTION.
C = the INCIDENT WAVE
A = the ANGLE OF INCIDENT
B = the ANGLE OF REFLECTION
D = the REFLECTED WAVE C D A B
When a WAVE strikes a barrier, it can be ABSORBED or REFLECTED.

24.
Refraction
Refraction: bending of a wave as it moves from one medium to another due to the speed of the wave changing as it enters the new medium
Refraction occurs when light passes into a transparent material.
When a light ray passes from air to water, it slows down and bends towards the normal.
Refraction occurs when a wave enters a new medium at an angle because the wave speed changes.

25. Diffraction Diffraction: the bending of waves around a barrier
Diffraction
Diffraction: the bending of waves around a barrier
- Light waves don’t diffract as much as sound waves do because the wavelengths of visible light are often much smaller than a barrier’s opening and matter slows light down.
- A wave is diffracted more when the wavelength is a similar size to the barrier opening. Therefore, sound waves travel through barriers more easily because they have a longer wavelength.

26.
Interference
Interference: the ability of two waves to combine and form a new wave when they overlap
Constructive- the crest of one wave overlaps the crest of another wave and form a bigger wave (more speed and amplitude). The waves bounce off of each other.
Destructive: the crest of one wave overlaps the trough of another wave and form a smaller wave.

27. Homework
Answer the Section 3 Assessment questions (#1-5) found on page 333 in your notebook.