國際課程課件系列之物理Wave-measurements-and-the-wave-equation

P7

WavesThis

lessonWhat

is

a

wave?Longitudinal

and

transverse

waves

Amplitude,

wavelength,

frequency

andperiod

of

a

wave

The

relationship

between

frequency

andperiodThe

wave

equationWhat

is

a

wave?YouTube

-

Water

bubble

in

Space

(zero

gravity)

/watch?v=xUnadiyPTks/watch?v=B01vktb2bj4WavesWaves

can

transfer

energy

andinformation

without

a

net

motion

of

thematerial

through

which

they

travel.They

involve

vibrations

(oscillations)

ofsome

sort.WavesWaves

can

transfer

energy

andinformation

without

a

net

motion

of

thematerial

through

which

they

travel.They

involve

vibrations

(oscillations)

ofsome

sort.Can

you

do

something

very

boringand

traditional………Can

you

copy

this

please?Transverse

wavesThe

oscillations

are

perpendicular

to

thedirection

of

energy

transfer.peakDirection

of

energy

transferoscillationtroughTransverse

wavesWater

ripplesLightOn

a

rope/slinkyEarthquakeLongitudinal

wavesThe

oscillations

are

parallel

to

the

direction

ofenergy

transfer.Direction

of

energy

transferoscillationcompressionrarefractionLongitudianl

wavescompressionrarefractionLongitudinal

wavesSoundSlinkyEarthquakeWavemeasurementsAmplitude

-

AThe

maximum

displacement

from

themean

(average)

position.amplitudeFrequency

-

fThe

number

of

oscillations/waves

in

onesecond.

Measured

in

Hertz.50

Hz

=

50

vibrations/waves

in

one

second.Wavelength

-

λThe

length

of

one

complete

wave.wavelengthWave

speed

-

vThe

speed

at

which

energy

is

transferredalong

the

wave330

m.s-1The

Wave

Equationv

=

fλv=

speed

(m/s)

λ

=

wavelength

(m)f

=

frequency

(Hz)vλf

x1)

A

water

wave

has

a

frequency

of

2Hz

and

a

wavelengthof

0.3m.

How

fast

is

it

moving?2)

A

water

wave

travels

through

a

pond

with

a

speed

of1m/s

and

a

frequency

of

5Hz.

What

is

the

wavelengthof

the

waves?3)

The

speed

of

sound

is

330m/s

(in

air).

When

Davehears

this

sound

his

ear

vibrates

660

times

a

second.What

was

the

wavelength

of

the

sound?4)

Purple

light

has

a

wavelength

of

around

6x10-7m

and

afrequency

of

5x1014Hz.

What

is

the

speed

of

purplelight?Some

example

wave

equation

questions0.2m0.5m0.6m/s3x108mWave