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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