WAVES

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# WAVES - PowerPoint PPT Presentation

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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Presentation Transcript

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
Infrared light
• Visible light
• Ultraviolet light
X-rays
• Gamma Rays
ROYGBIV
• RED
• ORANGE
• YELLOW
• GREEN
• BLUE
• INDIGO
• VIOLET
What 3 characteristics doAll Waves have?
• 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
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
Longitudinal wave do not have crests and troughs, instead they have what?
• COMPRESSIONS
• RAREFACTIONS
• The medium vibrates horizontally.
Surface Waves move both horizontally and vertically simultaneously, which produces what kind of movement?
• 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

Name the 4 ways waves interact.
• 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.

The picture on the left is constructive interference.

The picture on the right is destructive interference.

4. INTERFERENCE1.   CONSTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is greater than either of the waves alone.
2.   DESTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is less than either wave alone.
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

NODESStationary points of a standing wave.ANTINODESLoops of a standing wave where maximum oscillation of the medium occurs.
• Resonant Frequency
• Sometimes called Natural Frequency.
STANDING WAVESRESONANT FREQUENCY(or natural frequency)The frequency at which a standing wave occurs.