Nature of WavesLook @ pg. 602!

A wave is any disturbance that transmits energy through matter or empty space.

Example: water waves in the ocean

microwaves inside the microwave oven

light waves from the sun

radio waves transmitted to the radio

sound waves from the radio, telephone, & voices

Nature of WavesMost waves transfer energy by the vibration of particles in a medium.

A medium is a substance through which a wave can travel.

A medium can be a solid, liquid, or gas.

Question:You are a commander of a space station located about halfway between Earth and the moon. You are in the Command Center, and your chief of security tells you that sensors have just detected an explosion 61.054 km from the station.How long will it be before you hear the sound of the explosion?

Sound waves need a medium through which to travel. If there are no particles to vibrate, no sound is possible!

Electromagnetic waves, like visible light, can transfer energy without going through a medium.

Nature of WavesTypes of Waves:

Waves in which the particles vibrate in an up-and-down motion are called transverse waves.

The particles in transverse waves move perpendicular to the direction the wave is going.

The highest point of a transverse wave is called a crest.

The lowest point of a transverse wave is called a trough.

All electromagnetic waves are considered transverse waves.

Transverse wave…Transverse wave…

Draw this wave on the front of the “Nature of Waves” flap & label: crest and trough

Nature of WavesTypes of Waves:

In a longitudinal wave, the particles of the medium vibrate back and forth along the path that the wave moves.

A part of a longitudinal wave where the particles are crowded together is called a compression.

A part of a longitudinal wave where the particles are spread apart is called a rarefaction.

A sound wave is an example of a longitudinal wave. .

Longitudinal WaveLongitudinal Wave

Draw this wave on the front of the “Nature of Waves” Draw this wave on the front of the “Nature of Waves” flap & label: rarefactions and compressions.flap & label: rarefactions and compressions.

Properties of WavesThe amplitude of a wave is the height of the wave.

A wave’s amplitude is the maximum distance that the particles of a medium vibrate from its rest position.

Larger amplitude = more energy

Smaller amplitude = less energy

Properties of WavesA wavelength is the distance between any two crests or compressions next to each other in a wave.

The distance between two troughs or rarefactions next to each other is also a wavelength. Shorter wavelength = more energy

Longer wavelength = less energy

Amplitude and WavelengthAmplitude and Wavelength

Draw and label the properties of a wave: Draw and label the properties of a wave: amplitude and wavelength on the front of amplitude and wavelength on the front of the “Properties of Waves” flap.the “Properties of Waves” flap.

You can use pg. 608-609 if you need help.You can use pg. 608-609 if you need help.

Bell Work: 3/17/10Bell Work: 3/17/101.1. Draw and label a transverse wave. Be sure Draw and label a transverse wave. Be sure

that all parts are properly labeled.that all parts are properly labeled.2.2. Draw and label a longitudinal wave.Draw and label a longitudinal wave.3.3. __________ waves vibrate back and forth.__________ waves vibrate back and forth.4.4. ___________ waves vibrate up and down.___________ waves vibrate up and down.5.5. If you did not finish the last drawing we did If you did not finish the last drawing we did

yesterday in class, finish drawing and yesterday in class, finish drawing and labeling that as well.labeling that as well.

TCAP Practice Book #25-28 pg. 116-117TCAP Practice Book #25-28 pg. 116-117

Properties of WavesFrequencyFrequency is the is the number of wavesnumber of waves produced in a produced in a given given amount of time is called the frequency of a wave. is called the frequency of a wave.

Measure the frequency by Measure the frequency by countingcounting either the number either the number of of crestscrests or or troughtroughs that pass a point in a certain s that pass a point in a certain amount of time.amount of time.

Frequency is expressed in Frequency is expressed in HertHertz (Hz).z (Hz).HigherHigher frequency = frequency = moremore energy energy

Properties of WavesWaveWave speedspeed is the speed at which a wave travels. is the speed at which a wave travels.

Wave speed can be calculated by using the following Wave speed can be calculated by using the following formula:formula:

v = v = λ λ xx f f oror v = λ v = λ • • ff

v = wave speedv = wave speed

λ = wavelengthλ = wavelength

f = frequencyf = frequencyDetermine the wave speed of a wave that has a wavelength of 5 m and a frequency of 4 Hz. Express the units as m/s.

Wave InteractionsReflection happens when a wave bounces back after hitting a barrier.

All waves- including water, sound, and light waves- can be reflected.

Light waves reflecting off an object allow you to see the object.

Light reflects off surfaces the same way that a ball bounces off the ground.

If you throw the ball straight down against a smooth surface, it will bounce straight up.

If you bounce it at an angle, it will bounce away at an angle.

Wave InteractionsReflection (cont.)

A reflected sound wave is called an echo.

The light is reflecting off the mirror and back into your eyes so that you are able to see yourself.

How does the pencil look How does the pencil look broken?broken?

Wave InteractionsRefraction is the bending of a wave as it passes from one medium to another at an angle.

Rainbows are created when sunlight is refracted by water droplets.The water droplets separate white light into the colors of visible light.

Wave InteractionsThe bending of waves around a barrier or through an opening is known as diffraction.

Wave InteractionsThe result of two or more waves overlapping is called interference.

If you move a rope at certain frequencies, the rope appears to vibrate in loops.

The loops come from the interference between the wave you made and the reflected wave, thus resulting in a standing wave. Certain parts of the wave are always at rest position.

Wave InteractionsThe frequencies at which standing waves are made are called resonant frequencies.

When an object vibrating at or near the resonant frequency of a second object causes the second object to vibrate, resonance occurs.

A resonating object absorbs energy from the vibrating object and vibrates, too.

Tacoma Narrows Bridge AKA “Galloping Gertie” is a phenomenon, or an extraordinary event, that caused a lot of destruction because of resonance.

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