# WAVES - PowerPoint PPT Presentation

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WAVES. Chapter 12 Physics. Waves transfer what?. ENERGY!!!!. What are the two main types of waves?. MECHANICAL WAVES ELECTROMAGNETIC WAVES. Which type of wave requires a medium?. MECHANICAL WAVES Electromagnetic waves do NOT need a medium. What are 3 examples of Mechanical Waves?.

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WAVES

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Chapter 12

Physics

## Waves transfer what?

ENERGY!!!!

### What are the two main types of waves?

• MECHANICAL WAVES

• ELECTROMAGNETIC WAVES

## Which type of wave requires a medium?

MECHANICAL WAVES

Electromagnetic waves do NOT

need a medium.

### What are 3 examples of Mechanical Waves?

• Water waves

• Sound waves

• Seismic waves

### What are some examples ofElectromagnetic Waves?

• Microwaves

• Infrared light

• Visible light

• Ultraviolet light

• X-rays

• Gamma Rays

• ROYGBIV

• RED

• ORANGE

• YELLOW

• GREEN

• BLUE

• INDIGO

• VIOLET

• VIOLET

• RED

• Amplitude

• Wavelength

• Frequency

### What does the size of the amplitude of a wave tell us?

• HIGH AMPLITUDE = HIGH AMOUNTS OF ENERGY

• LOW AMPLITUDE = LOW AMOUNTS OF ENERGY

• Meters

• Lambda 

### What are the 3 units we can use for Frequency of a wave?

• Waves / second

• Cycles / second

• 1/s = Hertz (Hz)

### Frequency Example Problem

• A boy standing on a dock counts 20 waves

• pass by in 5 seconds. What is the frequency

• of the waves?

f = #waves / time

20 waves / 5 seconds = 4 Hz

### Frequency Example Problem #2

• If the frequency of the waves is increased

• to 8 Hz, how many waves will pass by the

• boy in 2 seconds?

f = #waves / time

8 Hz = #waves / 2 seconds

8 Hz x 2 seconds = 16 waves

### Name the 2 types of Mechanical waves.

• TRANSVERSE WAVES

• LONGITUDINAL WAVES

• TRANSVERSE

• COMPRESSIONS

• RAREFACTIONS

### How does the medium movewhen a longitudinal wave moves through it?

• The medium vibrates horizontally.

• Circular

### Speed of WavesWhat is the wave equation?

• V = f 

• speed = frequency times wavelength

### SPEED OF WAVESspeed = frequency x wavelength

v = f x λ

Example #1

A wave on a lake is traveling with a velocity of 8 m/s.

the frequency is 2 Hz. What is the wavelength of

this wave?

8 m/s = 2 Hz xλ

λ = 4 m

Speed of a wave example

http://www.acoustics.salford.ac.uk/schools/teacher/lesson1/lesson1interactive.html

• Reflection

• Refraction

• Diffraction

• Interference

### Explain reflection of a wave.

• Bouncing back of a wave after it strikes a boundary.

### Explain Refraction.

• The change in path of a wave when it moves into a medium of a different density.

REFRACTIONBending of waves due to a change in speed.Short tutorial/animation to watch.http://www.wiley.com/college/strahler/0471480533/animations/ch19_animations/animation2.html

### Explain Diffraction.

• The curving of waves around barriers and ability of waves to spread out in circular pattern after passing through a narrow opening. See picture below.

• Constructive

• Destructive

### Which of the pictures below is an example of Constructive Interference?

The picture on the left is constructive interference.

The picture on the right is destructive interference.

### Applet Interference by 3 wavessimultaneously.

Constructive interference applet

http://id.mind.net/~zona/mstm/physics/waves/interference/waveInterference1/WaveInterference1.html

Both Constructive/Destructive interference applet

http://id.mind.net/~zona/mstm/physics/waves/interference/waveInterference2/WaveInterference2.html

### Nodes and Antinodes are parts of what kind of wave?

• Standing Wave

### The frequency at which a standing wave occurs is called what?

• Resonant Frequency

• Sometimes called Natural Frequency.

The End!.