Waves, Electromagnetic Waves, Light, and Sound

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• Waves, Electromagnetic Waves, Light, and Sound

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Waves

• is a disturbance
• moves through a medium from one location to
  another location
• A medium is a substance or material which carries
  the wave.

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General Wave Properties

• All waves are traveling disturbances.
• All waves transfer energy from place to place.

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Parts of a wave

• Crest and Trough
• -The section of the wave that rises above the
  undisturbed position - crest
• -That section which lies below the undisturbed
  position - the trough

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Amplitude

• position of the medium to the top of a crest or
  trough.
• Height of the wave

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positive and negative amplitudes
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Different amplitudes
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Wavelength
crest to next crest, trough to next trough,
from the start of a wave cycle to the next
starting point Wave to wave
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Ex for wave length
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Types of Waves

• There are three types of waves  
• -Mechanical waves.
• -Electromagnetic waves
• -Matter waves

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Mechanical waves

• require a material medium to travel (air, water,
  ropes).
• These waves are divided into three different
  types.
• Transverse waves
• Longitudinal waves
• Surface waves

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Transverse Waves

• is perpendicular to the direction of wave
  propagation
• Ex light, heat, water waves.

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Longitudinal Waves

• is parallel to the direction of wave
  propagation

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Compression and Rarefaction

• Compression
• Wave that has no crests or troughs
• Region where the medium become crowded or dense
• Compress close together.
• Sound waves shock waves
• Rarefaction
• The less dense region

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Water Waves

• involve a combination of both longitudinal and
  transverse motions
• particle indeed travels in a clockwise circle as
  the wave passes.

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Electromagnetic waves

• do not require a medium to travel (light, radio

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Matter waves

• are produced by electrons and particles.

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Pulse and traveling or periodic wave

• a single vibration is produced is a pulse.
• moving regularly up and down, is a traveling or
  periodic wave .

 

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Measuring Waves

• The number of vibrations per second is called
  frequency
• Speed of the waveFrequency X Wavelength
• is measured in hertz (Hz).

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The Wave Formula

• Velocity Wavelength x Frequency .
  .
• V l x f
• Velocity(m/s), Wavelength (m), Frequency (hz)

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The Nature of Sound

• Sound is caused by vibrations
• Sound waves are Compression waves
• Cannot travel through a vacuum no particles to
  push around
• Travels faster through liquids and solids than
  gaseswhy?
• Travels faster through warmer than cooler
  substanceswhy?

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Properties of Sound

• Key Sound Terms
• Frequency How many wavelengths pass a point
  each second hertz (Hz) high frequencyhigh
  pitch humans 20-20,000 Hz
• Pitch How high or low a sound seems to be
• Intensity Amount of energy that flows through a
  certain area in a specific amount of time
• Loudness Human perception of intensity

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• the symbol f is frequency
• the symbol T is used for period,
• these equations are also expressed as

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Differences in Frequencies
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Wave speed

• Light wave- faster than sound
• Ex flying ball reaches your eyes before the
  sound wave created by the bat and ball
• Depends on the medium
• Ex sound waves travel faster in liquids than
  solid
• Ex Light waves travel slower in liquids and
  solids

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Calculating the wave speed

• Speed Wavelength Frequency
• Speed-v, Frequency-F
• And Wave length -

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The Nature of a Sound Wave

• Sound is a mechanical wave
• Sound is a Pressure Wave
• results from the longitudinal motion of the
  particles of the medium

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Compression and rarefaction

• -As the compression (high pressure)
• -rarefaction (low pressure)

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Sound

• Measuring intensity of Sound
• Intensity is the amount of energy in the wave
• Unit of intensity is the decibel (dB)
• Above 120 dB cause pain and hearing loss
• Doppler effect
• The change in pitch or wave frequency due to a
  moving wave source
• Examples
• Either the source or the observer can be moving

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Doppler effect

• Doppler effect can be observed for any type of
  wave
• Ex water wave, sound wave, light wave, etc
• the pitch of the siren sound was high after the
  car passed by, the pitch of the siren sound was
  low. That was the Doppler effect

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eardrum into vibration motion.
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Sound/Music

• Noise vs. Music
• Noiserandom patterns and pitches
• Musicsounds deliberately used in a regular
  pattern
• Musical Instruments
• String? vibrations of strings working with a
  resonator that amplifies the sound
• Brass and woodwinds? vibration of air in column
  working with a resonator holes and valves or
  changing the length of the air column
• Percussion? vibration of the membrane causes air
  inside to vibrate

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Sound

• Ultrasound
• Medicine? high frequency sound waves to detect
  and monitor such things as pregnancy, heart
  disease, and cancer
• can be used to break up kidney stones and gall
  stones

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Radio Communication

• Radio transmission
• Each station is assigned a unique frequency
  (called a carrier wave)
• FM (frequency modulation) AM (amplitude
  modulation) higher frequencies than AM
• Article page 405

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Behavior of Waves

• Types of Interference
• Occurs when two waves combine into one
• Constructive the wave gets bigger because the
  crest and trough overlap
• Destructive the wave gets smaller because a
  crest and a trough overlaps

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Properties of Sound

• Intensity
• Is the amount of energy that flows through a
  certain area in a specific amount of time.
• High intensity carries high energy
• Loudness
• Is the human perception of the intensity.
• The intensity of the sound increases, the
  loudness of the sound you hear increases.

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• Ultrasonic wave
• Humans cant hear sound frequencies above 20,000
  Hz, called ultrasonic waves.
• Used in medical diagnosis and treatment.
• Infrasonic waves
• Is also called subsonic wave
• Have frequencies below 20 Hz
• Too low to hear
• May feel them as a rumble inside your body

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• Resonance
• is the ability of the medium to vibrate by
  absorbing energy at its own natural frequency.
• Resonance helps amplify the sound created in many
  musical instrument
  
  

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• Music
• Is made of sounds that are deliberately used in a
  regular pattern.
• Musical instruments contain strings , membranes
  or columns of air- something that vibrates at its
  natural frequency to create a pitch.
• Natural frequency depends on the strings
  thickness and length and how tightly it is
  stretched