What is a Wave? Chapter 12 Section 3 Glencoe Pages 452-458.

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2 What is a Wave? Chapter 12 Section 3 Glencoe Pages 452-458

3 I. Types of waves A. What is a wave? 1. Wave – a disturbance that carries energy through matter or space  the matter moves very little  the energy moves

4 Most waves travel through a medium 2. Most waves travel through a medium a. medium – matter through which a wave travels  ripples in a pond move through water  sound waves travel through the air

5 Mechanical waves b. Mechanical waves – waves that require a medium to travel  almost all waves are of this type

6 Electromagnetic waves c. Electromagnetic waves – waves caused by electric and magnetic fields that do not require a medium  Electromagnetic spectrum of waves, consisting of: Radio waves, Microwaves, Infrared waves, Visible light, Ultraviolet waves, X-rays, and Gamma rays

7 Electromagnetic waves

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10 Wave Energy 3. Waves transfer energy  energy is the ability to do work  waves have energy therefore waves can do work example:water waves on a boat

11 Wave Energy Example: light waves on the eyes

12 Wave Energy Example: sound waves on your eardrum *Bigger waves carry more energy

13 Wave Energy 4. Energy may spread out as a wave travels - sound waves, ripples in a pond move out in circular patterns called wave fronts, and get bigger farther from the source and the energy spreads out along the entire wave front

14 B. Vibrations and waves 1. Most waves are created by a vibrating object 2. Vibrations involve a transformation of energy, generally between potential and kinetic

15 C. Transverse and longitudinal waves 1. Particles in a medium can vibrate up and down or back and forth 2. Waves are classified by the direction of particle movement

16 Transverse and longitudinal waves 3. Transverse waves – waves causing the particles of the medium to vibrate perpendicular to the direction the wave is traveling. Ex. Crowd doing the wave, light waves Link to waves

17 Transverse and longitudinal waves 4. Longitudinal waves – waves causing the medium particles to move parallel to the wave’s direction of travel  squeezing together (compression)  spreading apart (rarefactions) ex. Sound waves

18 Surface waves 5. Surface waves – occur at boundaries between different mediums  air and water - these waves move both in a transverse and a longitudinal way.

19 Wave Properties and Forms Chapter 12 Section 3: Holt Physics Continued

20 II. Two Basic Wave Forms A. Pulse wave – a single non-periodic wave  A single traveling wave  Example:

21 II. Two Basic Wave Forms B. Periodic wave – wave whose source is some form of periodic motion  Bouncing spring, wave machine  Example:

22 III. Wave properties A. Transverse waves look like a sine curve (looks like an “S” on its side) - example drawing – all parts labeled

23 I. Wave properties Transverse wave picture - sine waves with the shape of a sine curve - Waves whose particles move perpendicular to the direction of wave motion

24 B. Parts of a transverse wave 1. Crest – highest point on a transverse wave 2. Trough – lowest point on a transverse wave 3. Amplitude – greatest distance a particle is displaced from its normal resting position

25 B. Parts of a transverse wave 4. Wavelength – distance between 2 successive identical points on a wave  symbol = (lambda) measured in meters

26 C. Longitudinal waves 1. No crests or troughs 2. Compressions and rarefactions (stretched) - example drawing of longitudinal wave (click on picture)

27 C. Longitudinal waves Wave whose particles move parallel to the direction of wave motion Compressions – areas where the medium is squeezed together closer than at equilibrium Rarefactions – areas where the medium is stretched or expanded farther apart than at equilibrium One wavelength is from compression to compression or rarefaction to rarefaction

28 Longitudinal Waves Longitudinal waves examples  Example #1Example #1  Example #2Example #2

29 IV. Period, Frequency, and Wavespeed The source of the vibration determines the frequency Frequency (f)– number of wavelengths that pass a point in 1 second  measured in hertz (Hz)  named after Heinrich Hertz (1888)  1 Hz = 1 wavelength (vibration) per second  can hear 20 Hz (low)  20,000 Hz (high) Frequency of a vibrating object = frequency of a wave Frequency (f) = # of vibrations per second  # vibrations / time

30 IV. Period, Frequency, and Wavespeed Wavespeed = frequency x wavelength V (m/s) = f (hz) x (m) The wavespeed of a mechanical wave is constant for a given medium Period (T) – time required for one full wavelength to pass a certain point (measured in seconds)