Outcome 1 & 2 -notes SOUND & Wave Interactions.doc

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I) Outcomes 1 & 2 – SOUND & Wave Interactions

A. Sound (Video: ..\Waves Video.asx - 3:40-6:35)

1) Sound -Energy that causes the molecules of a medium to vibrate.

. . . is a longitudinal wave.

--Speed of sound – depends on the medium. . . sound is faster in most solids than in liquids and slowest in gasses.(Video: ..\ Waves Video.asx- 6:35-9:08)

[Higher density = lower speed / Higher elasticity (restoring forces) = faster speed]

i) In air = about 760 mph. Sound travels 0.2 mile per second. [So, sound travels 1 mile in 5 seconds]

ii) In water = about 3,300 mph iii) In rock = about 13,000 mph

2) Properties of sound:

a) Loudness: The intensity or loudness of a sound is determined by the Amplitude of a sound wave, OR how tall or short the wave is.

- Tall sound waves push hard against your ear drum (and vice versa).

- Measured in decibels.

b) Pitch: (Frequency)

The pitch (high or

low) is determined by the how wide the wavelengths are apart (which also determines frequency).

- Narrow wavelengths make the eardrum vibrate quickly (and vice versa).

c) Octave – Two times the

frequency of another note.

Illustration of loud and soft sounds

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B) Sound and Wave Interactions (how waves behave)

(Video: ..\Waves Video.asx - 12:10-16:44) 1) Absorption – Wave energy being stopped.

Example: Black shirt absorbing all visible light. 2) Transmission – Wave energy passing through a medium.

Examples: 1) Light through anything transparent 2) sound through air/water/solids

3) Reflection – Wave energy bouncing off of a barrier.

Examples: 1) Echoes 2)Your reflection in a mirror 3) A blue shirt is blue because it reflects blue and absorbs the other

colors.

4) Refraction – Wave energy that passes through a medium will change direction because it changes speed. Examples: 1) Light through a lens 2) “Broken pencil” in water 5) Diffraction – Wave energy bending around a barrier.

Example: Laser light spreading out around a pencil.

6) Interference – What happens when two or more waves arrive at the same time.

Two types: Constructive Interference (multiplies the energy) 

and Destructive Interference (negates the energy). (Video: Interference: ..\Waves Video.asx-16:44-18:50)

7) Resonance – The ability of an object to vibrate by absorbing energy from the object’s natural frequency.

(Video: ..\Waves Video.asx - 16:12-16:44) Examples: 1) Resonance boxes

2) The falling bridge video 3) breaking glass with sound

Illustration of Incident and Reflected Rays

..\Bridges - Tacoma Narrows Collapse.mov

(1:30-3:07)

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A)

SOUND

1)

Energy that causes the

molecules of a medium to

vibrate. . . is a longitudinal

wave.

(Video: ..\Waves Video.asx - 3:40-6:35)

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1) Sound - Energy that causes the molecules of a medium to vibrate.

. . . is a longitudinal wave.



Speed of sound –

depends on the

medium

. . .

Sound in a vacuum (bell jar):

(5)

Speed of sound – depends on the medium. . .

sound is faster in most

solids

than in

liquids

and

slowest in

gasses

.

(6)

Speed of sound – depends on the medium. . . sound is faster in most solids than in liquids and slowest in gasses.

[Higher density =

slower

speed / Higher elasticity

(restoring force) =

faster

(7)

(Higher density = lower speed / Higher elasticity = faster speed)



In air = about

760 mph

.

Sound in air travels about

0.2

(8)



In air = about 760 mph. Sound

in air travels about .2 mile per

second.

[So, sound travels

1mile

in 5

seconds]

(9)



In air = about 760 mph. Sound in air

travels about .2 mile per second.

[So, sound travels 1mile in 5 seconds]



In

water

= about 3,300 mph



In

rock

= about

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In air = about 760 mph.

In water = about 3,300 mph

In rock = about 13,000 mph

2) Properties of sound:

a) Loudness: The intensity

(or loudness) of a sound is

determined by the

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Amplitude

Normal resting position 2) Properties of sound:

a) Loudness: The intensity or loudness of a

sound is determined by the Amplitude of

a sound wave

,

OR

how

tall

or

short

the

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2) Properties of sound:

a) Loudness: The intensity or loudness of a sound is

determined by the Amplitude of a sound wave, OR how

tall

or short the wave is.

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a) Loudness: The intensity or loudness of a sound is

determined by the Amplitude of a sound wave, OR how

tall

or short the wave is.

- Tall sound waves push hard against your ear drum (and vice versa).

- Loudness is measured in units

called

decibels

.

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Loud sound

wave

Soft sound

wave

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- Tall sound waves push hard against your ear drum (and vice versa).

- Measured in decibels.

b) Pitch (aka

Frequency

):

The

pitch (high or low) is

determined by how

wide

the

wavelengths

are apart

(which also determines

frequency).

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Illustrations of a Sound Wave’s Pitch

b) Pitch: (Frequency)The pitch (high or low) is determined by the how wide or narrow the wavelength is (which also determines frequency).

- Narrow wavelengths (high

pitch) make the eardrum

vibrate

quickly

(and vice

versa).

Human hearing

range = 20 - 20,000

Hz

Bass tests 25- 65 Hz:

http://www.youtube.com/

watch?v=1l79-fPVgkE&feature=related

Low pitch

sound

High pitch

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60 – 14,000 Hz:

http://www.youtube.com/watch?

v=FB_V0_wMnGI

Dogs hearing range =

up to 40,000 Hz

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c) Octave –

Two times the

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c) Octave – Two times the frequency of another note.

B) Wave Interactions – “

how

waves behave

.”

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B) Wave Interactions – “how waves behave.”

1)

Absorption

– Wave energy

is

stopped

.

Examples:

For

Light:

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B) Wave Interactions – how waves behave. 1) Absorption – Wave energy being stopped.

Example: Black shirt absorbing all visible light.

2) Transmission

– Wave

energy

passing through a

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2) Transmission – Wave energy passing through a medium.

Examples:

1)

Light through anything

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2) Transmission – Wave energy passing through a medium.

Examples:

1) Light through anything transparent

(clear)

2)

Sound through

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Incident (incoming)

reflected (outgoing)

Examples: 1) Light through anything transparent 2) sound through air/water/solids

3)

Reflection

–

Wave energy

bouncing off of a barrier

.

Examples:

1)

Sound

Echoes

2)

Your reflection in a mirror

Illustration of Incident and Reflected Rays

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Examples: a) Sound Echoes

b) Your reflection in a mirror

c) A

blue

(or

red

or

green

)

shirt is

blue

because it

reflects

blue

and

absorbs

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Examples: 1) Echoes 2)Your reflection in a mirror 3) A blue shirt is blue because it reflects blue and absorbs the other

colors.

4)

Refraction

– Wave energy

that

passes through a

medium

will

change speed

causing it to

change

direction

.

(Video ..\Waves Video.asx from13:37-14:06)

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4) Refraction – Wave energy that passes through a medium will change speed causing it to change

speed.

Examples:

1)

Light through a

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Examples: 1) Light through a lens 2) “Broken pencil” in water

5)

Diffraction

– Wave energy

bending around a barrier

.

(Video ..\Waves Video.asx from 14:06-14:26)

Diffraction: http://www.youtube.com/watch?v=kH57Di7Sj0c

Example:

Laser light

spreading out around a

pencil

.

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5) Diffraction – Wave energy bending around a barrier.

Example: Laser light spreading out around a pencil.

6)

Interference

– What

happens when

two or more

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6) Interference – What happens when two or more waves arrive at the same time.



Two types:

Constructive

Interference

(

amplifies

the energy) &

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Destructive

Interference

(

cancels

the energy).

Destructive interference: http://www.youtube.com/watch? v=J4qFPComzoo

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6) Interference – What happens when two or more waves arrive at the same time.

Two types: Constructive Interference (multiplies the energy) and Destructive Interference (negates the energy).