7.1 Waves Mr. Perez. What are waves? Waves are disturbances that move through matter or space Waves...
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Transcript of 7.1 Waves Mr. Perez. What are waves? Waves are disturbances that move through matter or space Waves...
7.1 WavesMr. Perez
What are waves?
Waves are disturbances that move through matter or space
Waves TRANSFER ENERGY, NOT MATTER from place to place
Waves are made by vibrating objectsThe energy in the vibrations transfer the waves
outward
Types of Waves
Mechanical waves- waves that can only travel through matter and not through spaceTransverse wavesCompressional (longitudinal)
waves
Electromagnetic waves- waves that can travel through both matter and space
Transverse waves
Type of mechanical wave
Causes particles in matter to move at right angles to the direction in which the wave travels
Compressional (longitudinal) waves
Type of mechanical wave
Causes particles in matter to move back and forth along the same direction in which the wave is traveling
Seismic waves
Type of mechanical wave
Waves move through the ground during an earthquakeSome are compressional
(longitudinal) and others are transverse
Rolling waves: cause the ground to move up and down and back and forth
Electromagnetic waves
Type of transverse wave
Contain electric and magnetic parts that vibrate up and down perpendicular to the direction the wave travels
Light, radio waves and X rays are some examples
Properties of Waves
All waves have properties that depend on the vibrations that produce them1. Wavelength
2. Frequency
3. Amplitude
4. Speed
Wavelength (λ)
The distance between any point on a wave and the nearest point just like it Transverse: crest to crest or trough to troughLongitudinal: compression to compression or
rarefaction to rarefaction
Measured in meters (m)
Frequency
Number of wavelengths that pass by a point each second
Measured in Hertz (Hz)1 Hz = 1 wavelength
per second1 Hz = 1/s
Amplitude
Maximum distance that matter moves as the wave passesTransverse: top of crest or bottom of trough to
resting positionLongitudinal: more squeezed together compressions
and more spread apart rarefactions
Amplitude and Energy
The larger the amplitude of a wave, the more energy the wave carries
Speed
How fast a wave travels
Measured in meters per second (m/s)
Wavelength formula:
Waves can change direction
When you see your own reflection, light is changing direction back at you
Waves can also travel from one material to another
REFLECT- bounce off a surface
REFRACT- bend
DIFFRACT- bend around an obstacle
Law of reflection
The angle that the incoming wave (i) makes with the normal equals the angle that the outgoing wave (r) makes with the normal
Refraction
Speed of a wave depends on the properties of the material through which it travelsChange in speed causes waves to bend
Refraction is the change in direction of a wave when it changes speed as it travels from one material to another
Diffraction
Bending of waves around an objectDepends on the size of the obstacle
The bigger the wavelength compared to the size of the obstacle, the amount of diffraction increases
Particles and Waves
Both particles and waves transport energy from one place to another
However,Particles have mass and volume and can carry an
electric chargeWaves have wavelength, frequency, amplitude
Links
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/visiblelight_solarsystem/wavesact.shtml
http://www.classzone.com/books/ml_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html
http://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html
References
Florida Science Grade 7, Glencoe Science & McGraw Hill Publishing
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