Waves Notes

Waves Notes

•Ch. 10• P. 290

(1-4)• P. 296

(1-7)• P. 303

(1-5)•Ch. 11

• P. 327 (1-6)

•Ch. 12• P. 354

(1-3)P. 360 (1-7)

•Ch. 13• P. 384

(1-5)

Vocabulary

Waves Notes• LINEAR MOTION= motion from

one point to another without repeating.– Distance– Time– Speed– Acceleration

• HARMONIC MOTION= motion that repeats over and over.

HARMONIC MOTION • Cycle (cyclic motion) = a unit of motion

that repeats. • Oscillator (oscillating system) = a

system that shows harmonic motion. • clocks• solar system• Seasons• music & musical instruments• cell phones• fm radio

• Period = time it takes for one cycle to occur.

Frequency= the number of cycles per second.

unit = Hertz (Hz) 1 Hertz = 1 cycle/second ex: human heartbeat = ½ to 2 beats per

second ex: human voice = 100 to 2000 cycles per

second

Amplitude

• a measure of how large the cycle is.

• This is the energy of a wave.ex: waves = height of the wave sound = volume

WAVESTransfer energy from place to place

without transferring matter

• a disturbance in a medium. • medium = matter that are able to

carry a wave.– ex: air carries sound waves– water carries waves

QUESTION: Can sound travel in space, in other words, could you hear in outer space?

ANSWER: NO! Sound requires a medium to carry its energy. Since matter does not exist in space the sound energy

would have nothing to travel on.

Transverse Waves• = oscillations that are perpendicular

(90º) to the direction the waves is moving.

• oscillation^ wave motion >

ex: water, light, S-waves in an earthquake

Longitudinal (compression) Waves

• = oscillations that are in the same directions as the motion of the waves.

• oscillation> wave motion >

• ex: sound, shock waves, P-waves -- earthquake

NOTE CHECKTAKE 2 MINUTES:

With a partner, check each other’s notes to be sure both

filled in all blanks

WAVESCan be:

transverseMatter moves:

@ right angles to wave directionWavelength

is measured: Crest to

Crest

Examples:Wave on a ropeWaves on

a lake

Can be:compressiona

lMatter moves:

Along wave directionWavelength is

measured: Compress

ion to Compress

ion

Examples:Sound wavesShock waves

PROPERTIES OF WAVES

WAVE TERMS• Frequency (f) = waves per second

(measured in Hertz)– known as Pitch in sound & music

• Amplitude = the height of the waves, the energy of the wave.– Measured from the resting position

to the crest.

• Wavelength (λ) = the length of one cycle. Distance from a point on a wave to the identical point on the next wave.

Which of the graphs has an amplitude of 10

centimeters?

5

31

Name five parts of a wave:1. __________________________________2. __________________________________3. __________________________________4. __________________________________5. __________________________________

Compare and contrast the 2 types of waves:1. Both = _______________________________2. Matter = ______________________________

3. Matter = ______________________________A wave is =1. _____________________________________

WAVE SPEED• Speed = the velocity the wave is

traveling.• velocity = wavelength x

frequency• v = λ x f• units

f = Hertz (Hz)λ = meters (m)v = meters/second (m/s)

Ex: An ocean wave has a frequency of 2 Hz and a speed of 20 m/sec. What is the wavelength of this wave?

λ = v/f λ = 20 m/s ÷ 2 Hz = 10 m

Examples of the Speed of Waves

• Speed of Light

300,000,000 m/s

300,000 km/s

186,000 miles/s

NOTE CHECKTAKE 2 MINUTES:

With a partner, check each other’s notes to be sure both

filled in all blanks

Examples of the Speed of Waves

• Speed of Sound

– Approx 340 m/s

– Approx 770 miles/hr– This will vary a great

deal due to temperature and atmospheric pressure

•Calculate the Speed of Sound

WAVES INTERACTIONSwhat results from waves

hitting objects• Reflection = The wave can bounce

off and go in a new direction.• Angle of Incidence = inbound

angle• Angle of Reflection = outbound

angle

• measured from the perpendicular and both angles are EQUAL

Which is the angle of incidence?Which is the angle of reflection?

Refraction = The wave can pass straight into and through the obstacle and are bent due to the change in density of the medium.

Diffraction = The wave can bend around or through holes in the obstacle.

Absorption = The wave can be absorbed and disappear.

NOTE CHECKTAKE 2 MINUTES:

With a partner, check each other’s notes to be sure both

filled in all blanks

WAVE INTERFERENCE• when 2 or more waves meet.

• Constructive Interference = When waves meet “in phase” trough to trough or crest to crest. The resulting waves become larger.

• ex: Sound = resonanceResonating Chambers = sinuses,

guitar, musical instrumentsWind Tacoma Narrows Bridge collapse in the

1940s

Tacoma Narrows Bridge

“in phase”

WAVE INTERFERENCE• Destructive Interference = When

waves meet “out of phase” crest to trough. The resulting waves become smaller or even cancel each other.

• ex: Dissonance = sound waves meet out of phase and noise results.

“out of phase”

THE DOPPLER EFFECT • radar speed detectors• metrology to detect wind speeds & on

coming weather fronts• very noticeable in auto racing

• Approaching Object = sound wave are compressed due to the speed of the approaching object thus increasing the frequency or pitch of the sound of the object.

• Departing Object = sound waves are stretched because the object is moving away from the listener thus decreasing the frequency or pitch of the sound of the object.

NOTE CHECKTAKE 2 MINUTES:

With a partner, check each other’s notes to be sure both

filled in all blanks

THE ELECTROMAGNETIC SPECTRUM

• Electrons = the negatively charged particle in the atom is involved in light.– Electrons can absorb energy by various

ways causing them to jump to a higher energy level(s).

– Then they give off energy in the form of light when they move from the higher to lower energy level(s).

Parts of the electromagnetic spectrum

• Radio waves Longest Wavelength Lowest Frequency

• Microwaves• Infrared• Visible Light

– ROY G BIV• Ultraviolet• X-rays• Gamma rays Short Wavelength Highest Frequency

THE ELECTROMAGNETIC SPECTRUM

• Radiowaves(1 km to 30 cm)

– ex: AM & FM radio, TV signals

• Microwaves (30 cm to 1 mm)

– ex: microwave ovens, cellular communication

• Infrared (1 mm to 70 nm)

– ex: heat, sensors, guidance systems

• Visible Light (70 nm - 400 nm)

– ex: ROY G BIV

• Ultraviolet– ex: sunburns,

harmful to eyes, disinfect by killing bacteria

• X-Rays– ex: medical &

dental uses, inspect metal welding

• Gamma Rays– ex: originate

from the sun, atomic radiation

ROY G BIV • Red Longest wavelength Lowest frequency

• Orange• Yellow• Green• Blue• Indigo• Violet Shortest wavelength Highest

frequency

Visible Light • Optics = the study of light• Lasers = a single frequency of light

COLOR

• Primary Colors of Light

the color of transmitted light you see.

The light source–Red –Green –Blue• Red + Green + Blue =

White

COLORPrimary Colors of

PigmentA pigment is a colored

material that is used to change the color of other substances.

Reflected light color–Magenta–Yellow –Cyan • Magenta + Yellow + Cyan = Black

Computer Settings• pixel = dot = 3 numbers to assign the color

(0-256)

• Red, Green, Blue = RGB – ex: (0, 0, 0) = black

• 256 x 256 x 256 = 16,777,216 *possible different colors

The Eye• Lens = Tiny muscles around the eye

change the shape of the eye to focus the image when light passes through.

• Iris = The colored part of the eye that controls the amount of light entering the eye.

• Retina = A membrane lining the inside of the back of the eye composed of light sensitive receptors that are stimulated by the different wavelengths of light that makeup the image.

The Retina • Rods = Rod-shaped receptors

involved in night vision, peripheral vision (corners of the eyes) and making out the outline of objects.

• Cones = Cone-shaped receptors that contain color-sensitive pigments to detect red, blue, green and all their combinations.

Optical Illusion• seen images that “trick” the brain

into observing something that is not real.

Mirage• A false image in the distance produced by

the refraction of light through air layers of different densities.

Ex. The appearance of water in the distance

Mirage

SOUND • a pattern of air oscillations consisting of

areas of high pressure to low pressure. Sound consists of longitudinal (compression) wave thus it is impossible for sound to travel in space.

• Acoustics = the science or study of sound

• Amplitude = Loudness or Volume measured in Decibels (dB)

Decibels (dB) • 10 – 15 dB whisper (3 ft away)• 65 dB normal conversation (3 ft

away)• 70 dB city traffic• 90 dB jackhammer (10 ft away)• 120 dB threshold of physical pain

• 90 dB is 2x louder than 70 dB

Frequency (Pitch)– 20 Hz thunder– 100 Hz bass guitar– 500 Hz average male voice– 5000 Hz highest note on a piano– 10,000 Hz jet turbine engine– 20,000 Hz highest human limits

• human range 20 to 20,000 hertz (best 100 to 2000) *test ???

Speed of Sound• approx. 340 m/s or 770 mi/hr (in

air)• Calculate • speed varies greatly based on the

density of the medium

• ex: in air factors include altitude, humidity and temperature

Supersonic

• super = above• sonic = sound• motion that is faster than the speed

of sound.

Ultrasound• Medical use of sound waves to give

internal images of the human body.• Sonogram = Images of the baby

during pregnancy.