We are beginning a new unit:Waves, Light, & Sound

Introductory Video

Today we will be introduced to waves. The next two days we

will try a new method of learning. We will perform a variety of

experiments learning about waves BEFORE we read about them.

What are waves?

The Sweet Wave

WAVES

Carries energy from one place to another

Classified by what they move through 1. Mechanical Waves

the energy is transferred by vibrations of medium

(medium = matter)ex/ ocean waves move through water

2. Electromagnetic waves (EM Waves)the energy moves through disturbances in the electromagnetic field.

a disturbance that transfers energy

WAVE STRUCTURE

CREST (peak)AMPLITUDEresting to max peak

WAVELENGTH

TROUGH

Basic Properties of WavesAmplitude

Wavelength

Frequency

Hertz

AMPLITUDE

The maximum distance the medium vibrates from the rest position

Gives indication of “power” or “strength” of wave(magnitude of earthquake = Richter scale)

Does not affect velocity of wave

Determines loudness (sound) or brightness (EM wave)

Which has a larger amplitude?

WAVELENGTH Distance between any two corresponding parts of a wave

crest-crest, trough-trough,expansion-expansion, compression-compression

Determines what colorswe see; what notes we hear (pitch)

Shorter wavelengths have more cycles per minute because they aren’t as long

Which has a shorter wavelength?

FrequencyThe number of waves that pass a given point in a certain amount of time.

AKA number of vibrations per second.

Frequency measured in hertz (Hz).

Which has a higher frequency?

SPEEDthe rate at which the energy travels; speed & direction

Depends on mediumMechanical waves travel faster through dense mediums

EM Waves are faster through less dense mediums

MECHANICAL WAVES

travel through & gradually lose energy to that medium

Examples:water, sound, rope, & spring waves

Mechanical Media:water, air, rope, spring

require a medium (the material through which the disturbance is

moving) to transmit energy

Making a pulse

MECHANICAL WAVESClassified by how medium vibrates

Pulse = direction of energy transfer

           

           

Vibration = direction of vibration of medium relative to pulse

3 types: Longitudinal, transverse, surface

MECHANICAL WAVESClassified by how medium vibrates

Longitudinal Waves:Vibration is in the same direction as wave

pulse (parallel to wave pulse)

Transverse Waves:Vibration is at 900 (right angles) to wave pulse

Surface Waves:Vibration is circular Ex/ Ocean waves; surface waves

TRANVERSE WAVES

Sideways or up & down

Examples:S-type earthquake waves

Electromagnetic (EM) or light waves

Vibration is perpendicular to the direction of the motion of the wave

           

LONGITUDINAL WAVES

Back and forth (compression & rarefraction)

Also called compression or pressure wave

Examples:

P-type earthquake waves

Sound waves

Vibration is parallel to the direction of the motion of the wave

Rarefraction (expansion)

Compression

Compressional WaveMatter vibrates in the same direction as the wave travels.

Example: Slinky

Compressional waveThe parts,where the coils are close together are called compressions, the parts where the coils are spread out are called rarefactions.

Combinations of wavesSurface waves are a combination of transverse and longitudinal waves.The waves occur at the surface between water and air.