Ch. 11 Waves

11.1 Nature of Waves

11.2 Wave Properties

11.3 Wave Interactions

14.1 Nature of WavesRelate waves and the transfer of energy

Distinguish between transverse waves and longitudinal waves.

Predict the motion of a medium as a wave of energy passes through it.

Infer the energy content of a longitudinal wave.

There will be a quiz at the end of this lesson(take good notes)

Waves and Energy Transfer

Wave TermsWave - a disturbance that transfers energy through

matter (a medium) or space

Medium - a substance through which a wave passes(examples: sound through air, water, steel)

** Sound must have a medium to travel through. Soundwaves cannot travel in a vacuum.

When the fish gave energy to the cork by nibbling onthe worm, that energy shows up as the ripples in the water. (What is the medium in this situation?)

Types of Waves

A transverse wave is one in which the direction of themotion causing the wave is at a right angle to the direction of the motion of the wave.

Direction of motion

Directionof thewave

900

Motion of Energy

Parts of a transverse waveCRESTS

TROUGHS

The highest pointin a transverse wave

The lowest part ofa transverse wave.

) ) ) ))) ) ) ) ))) ) ) ) )))

In a longitudinal wave, the direction of the motion ofthe wave is the same as the direction of motion of themedium.

Direction of motion of the wave

Direction of motion of the medium

….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . .….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . .….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . . ….. . . . . .

In a longitudinal wave the particles of the medium willvibrate along a line. As the wave travels through themedium these particles are close together then far apart.When particles are close this is a COMPRESSSION.When they are far apart this is a RAREFACTION.

compressions rarefactions

Sound travels through a medium in longitudinal waves.

How does that work?

As you speak, air passes your vocal cords at certain speedscausing them to give energy to the air surrounding them.This energy is transferred to the air around your vocal cords(the medium) and through a series of compressions and rarefactions it travels through the air to your ear drum. Thevibrations are picked up by your ear drum and cause the bones in your inner ear to vibrate. Your brain changes it tothe sounds you hear.

) ) ) ) ) ) )

Sound actually travels in longitudinal waves in all directions.

Wave Properties

Wave Behavior

Are all waves the same? Actually, the size, speed, andshape of each wave are different. However, they do sharecommon characteristics.

All waves: 1. Transfer energy

2. Have height, speed, length, and frequency.

Wave Properties (cont)

Line of origin

crestWave length

trough

Wave length

Wave height

Definitions

Wavelength - (transverse waves) the distance betweentwo consecutive crests or two consecutive troughs.

(longitudinal waves the distance betweentwo consecutive compressions or two consecutive rare-factions.

Amplitude - Amplitude is the vertical distance (height)between the line of origin and each crest or each trough.

amplitude

Definitions (cont)

Frequency - The number of wavelengths that pass a given point in a given amount of time such as per second.

The unit for frequency is the hertz (Hz)1 wave per second = 1Hz

A

B

Wave B has agreater frequencythan Wave A

Definitions (cont)Wave Speed - Frequency and wavelength determinethe speed of a wave or how fast the wave approachesa given point.

Formula:

speed = frequency x wavelengthUnits:

m/s = Hz x meters

Wave height - the distance from the bottom of a trough to the top of a crest.

Review

Define transverse wave?

Define longitudinal wave?

What is a wave?

Terms that go with transverse waves:crest, trough

Terms that go with longitudinal waves:compression, rarefaction

Define: amplitude, frequency, wave height, wave speed hertz (Hz)

Your Quiz1. The transfer of energy through a medium is a _____________.

2

3

4 5

6

2 - 6 Use the diagram above to name the parts of a wave.7. In a sound wave where the particles of air are close together is a___________________.8. A _____________________ wave has rarefactions.

9. The unit for frequency is the _____________.

10. A wave with high amplitude has more / less energy than one with low amplitude.

wave

crest

trough

amplitudewave height

wave length

compressionlongitudinal

hertz (Hz)

-10 for each X

The

end ! !

Stay tuned for 14.3 Wave Interactions