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Vibration – a wiggle in time For example: moving back and forth in the same space, ie ., pendulum. **A vibration exists over time .* *. Wave – a wiggle in space and time For example : light and sound **A wave exists over space and time **. Major parts of a wave:.

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slide1

Vibration – a wiggle in timeFor example: moving back and forth in the same space, ie., pendulum. **A vibration exists over time.**

wave a wiggle in space and time for example light and sound a wave exists over space and time
Wave – a wiggle in space and timeFor example: light and sound**A wave exists over space and time**
major parts of a wave
Major parts of a wave:

Midpoint (Equilibrium)

crests and troughs
Crests and Troughs

Crest (high point)

Trough (low point)

how sound occurs
How sound occurs?
  • Sound is a fascinating phenomenon. When something vibrates in the atmosphere, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air. Ourears pick up these fluctuations in air pressure and translate them into electrical signals the brain can process.Electronic sound equipment works the same basic way. It represents sound as a varying electric current.
amplifier
Amplifier
  • Any device that simply produces a better quality and more powerful version of the audio signal.
frequency f
Frequency (f)

how often a vibration occurs

(# of crests per second)

vibrations per second

heinrich hertz
Heinrich Hertz

Heinrich Hertz demonstrated radio waves in 1886.

The unit of frequency is the Hertz.

1 vibration per second = 1 Hertz

Kilohertz= 1000 v/sec

Megahertz= 1000000 v/sec

How does a radio work?

frequency and period
Frequency and Period
  • Frequency and period are reciprocals of each other.
  • Frequency (f) = 1  period
    • f = 1/T
  • Period (T) = 1  frequency
    • T = 1/f
25 3 wave motion
25.3 Wave Motion
  • Sound and light waves move.
  • As waves move, matter is NOT passed along them.
for example
For example:

When you create a wave with a rope, it is the disturbance that moves along the rope, not the rope itself.

25 4 wave speed
25.4 Wave Speed

How fast a wave moves depends on the medium of the wave.

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Wave speed is related to the frequency and wavelength of the wave.

v = f*

Wave speed (m/s) =

frequency (Hz) X wavelength (m)

example
Example:

What is the speed of a wave with a frequency of 100 Hz and a wavelength of .025 meters?

answer
Answer:

v = fλ

Speed = 100 Hz X .025 m

Speed = 2.5 m/s

How does satellite tv work?

25 5 transverse waves
25.5 Transverse Waves

Waves produced when the motion of the medium is at right angles (PERPENDICULAR) to the direction in which the wave travels.

EX: Fishing bobber in a lake

25 6 longitudinal waves
25.6 Longitudinal Waves

Waves produced when the particles move ALONG (PARALLEL) the direction of the wave rather than at right angles to it

EX: Sound Waves

25 7 interference
25.7 Interference

overlapping waves

Interference Patterns: patterns formed when waves overlap

2 types of interference
2 types of interference:
  • constructive –

reinforcing interference

when waves align at the crests and troughs

**individual effects are increased**

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Destructive– cancellation interference

when the crest of one wave aligns with the trough of another

**their individual effects are reduced**

the doppler effect
The Doppler Effect
  • Christian Doppler

(1803-1853)

  • Change in frequency due to the motion of a sound source
the doppler shift
The Doppler Shift

Blue shift = frequency increases as it approaches

Red shift = frequency decreases as it leaves

blue shift red shift
Blue ShiftRed Shift

Lower frequency

Higher frequency

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Sonic BOOM– the sharp crack heard when the shock wave that sweeps behind a supersonic aircraft reaches the listener.

A slower aircraft sends sound wave crests one at a time and we hear it as a continuous noise.

sound

Sound

Chapter 26

what causes sounds
What causes sounds?

Answer:

vibrations

26 1 the origin of sound
26.1The Origin of Sound

All sounds are made by the vibration of material objects.

slide30
A vibrating source sends a disturbance through a surrounding medium (such as air) in the form of longitudinal waves.
pitch
PITCH

term that refers to how high or low sound appears to be

Is it possible to shatter glass with your voice?

slide32

High # of vibrations =

high frequency = high pitch

EX: piccolo

Lower # of vibrations =

lower frequency = lower pitch

EX: tuba

humans can hear the range from
Humans can hear the range from

20 - 20,000 Hz

Ultrasonic – sound waves above 20,000Hz

Infrasonic – soundwaves below 20 Hz

26 2 the nature of sound
26.2 The Nature of Sound
  • When a noise occurs, sound travels in all directions
26 3 media that transmit sound
26.3 Media that Transmit Sound

Any medium that waves travel through; may be solids, liquids or gases

Usually, sounds are emitted through air, but they can also pass through solids and liquids

different mediums carry waves at different speeds
Different mediums carry waves at different speeds
  • Solids and liquids are generally much better conductors of sound than air

EX: ever heard motor boats under water?

26 4 the speed of sound
26.4 The Speed of Sound
  • Sound travels MUCH slower than light

EX: lightening and thunder

  • The speed of sound at room temperature is 

340 m/s

26 8 resonance
26.8Resonance

Resonance– a phenomenon that occurs when the frequency of forced vibrations on an object matches the object’s natural frequency, and a dramatic increase in amplitude results

resonance
Resonance

Resonance can occur in structures

EX: marching over bridges

swinging bridges by wind

26 9 interference
26.9Interference

Interference occurs in sound waves.

Interference can occur “in phase” (constructive) or “out of phase” (destructive)

EX: announcer at a football stadium

Ripple Tank

26 10 beats
26.10Beats

Beat – periodic variation in the loudness of sound (different frequencies)

EX: musical instruments out of tune

Musical Beats

example1
Example

What is the beat frequency when a 400 Hz and a 405 Hz tuning fork are sounded together?

Answer:

Change in frequency = 5 Hz

Therefore, the beat frequency is 5 beats per second

light

LIGHT

Chapter 27

light1
LIGHT
  • we see objects because light bounces off them
  • Light is energy that is emitted by vibrating electric charges in atoms that travel in waves
27 2 the speed of light
27.2 The Speed of Light

Speed of light = extra distance traveled

extra time measured

= 300,000,000 km / 1000 sec

= 300,000 km/sec

27 2 the speed of light1
27.2 The Speed of Light

light year – the distance traveled by light in one year

≈ 9.5 x 1012 km

27 3 electromagnetic waves
27.3 Electromagnetic Waves
  • Waves by which light energy travels
  • All are radiated by vibrating electrons within an atom
27 7 polarization
27.7 Polarization

Light waves are transverse waves.

Polarization – the filtering out of all vibrations in a transverse wave, such as a light wave, that are not in a given direction

slide50

Reflection – bouncing off

  • Refraction – penetrating (goes through) and bends