Natural Science

1
Natural Science

• Chpt 11 12
• Spring 2004

2
Physical Science

• Chpt 14 and 15
• Spring 2007

3
Chapter 14

• Sound Waves

4
Vibrations and Waves

• Wavelength
• Amplitude
• Frequency wave crest/time

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Wave Motion

• Wave speed wavelength x frequency
• Transverse waves (sideways)
• Longitudinal waves (compression)

7
Sound waves

• Always longitudinal
• Speed of sound slow in air (340 meters/sec) not
  at all in vacuum faster in liquids very fast in
  solids

8
Sound Wave Applet
9
Reflection of sound

• Acoustics study of sound properties
• Hard surfaces reflect well (echo)
• Soft surfaces absorb sound

10
Resonance

• Natural frequency incident frequency
• Amplitude increases
• Constructive interference

11
Interference

• Constructive amplitude increases (reinforcement)
• Destructive amplitude goes to zero
  (cancellation)
• Fourier Transform (phase)
• Standing waves incident and reflected waves in
  phase

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15
Doppler Effect

• Moving source of sound
• Moving toward receiver - wavelength shortens
• Moving away from receiver - wavelength lengthens

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Wave Barriers

• Bow waves
• Sonic booms

18
Musical Sounds

• Generally a complex of fundamentals and harmonics
  - emphasized by resonator
• Bassoon is one of few instruments that produces
  only a fundamental
• Humans hear 20 to 20,000 hertz

19
Chapter 12

• Light Waves

20
Chapter 15

• Light Waves

21
Electromagnetic spectrum

• Gamma rays
• X-rays
• Ultraviolet
• Visible 400-800 nm
• Infrared
• Microwaves
• Radio TV

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Speed of light

• 300,00 km/sec in vacuum c186,000 miles/sec
• In water speed 0.75c
• In glass speed 0.67c
• In diamond speed 0.41c

24
Color

• Red 800 nm violet 400 nm
• In reflection and transmission all colors are
  absorbed except the visible one. If all colors
  are absorbed the apparent color is black
• White no colors absorbed
• When paints are mixed it is subtraction of
  apparent wavelengths

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Colors
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Colored lights

• When colored lights are mixed the result is
  additive
• Primary colors red, green, and blue

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Color Addition
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Polarized Light

• Light is a transverse (sideways) wave
• Normal light is transverse in 360 degrees
• Polarization removes light in certain transverse
  planes

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Polarizing filters
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Laser

• Normal light is composed of many frequencies of
  light mostly out of phase
• Laser light consists of only one frequency of
  light and it is in phase
• Coherent, monochromatic, collimated

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Reflection

• Angle of incidence angle of reflection
• Mirrors and recognition of yourself
• Diffuse reflection
• Polished reflection

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Refraction

• Bending of direction of light due to difference
  in transmission speed in media
• Critical angle
• Dispersion

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