Electromagnetic spectrum
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Electromagnetic Spectrum. LIGHT Principles of Physics. Electromagnetic Spectrum. Waves created by fluctuating electric and magnetic fields Transverse waves Can travel in a vacuum – do not need a medium Travel at the speed of light in a vacuum (c = 300,000,000 m/s)

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Electromagnetic Spectrum

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Electromagnetic Spectrum

LIGHT

Principles of Physics


Electromagnetic Spectrum

  • Waves created by fluctuating electric and magnetic fields

    • Transverse waves

    • Can travel in a vacuum – do not need a medium

    • Travel at the speed of light in a vacuum

      (c = 300,000,000 m/s)

  • Organized by frequency and wavelength


  • http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=35


3.84x1014 Hz

4.82x1014 Hz

5.03x1014 Hz

5.20x1014 Hz

6.10x1014 Hz

6.59x1014 Hz

7.69x1014 Hz

Red Orange Yellow Green Blue Violet


Radio, Micro, and Infrared Waves

  • Longest wavelength and lowest frequency

  • RADIO WAVES ARE NOT SOUND WAVES

  • Provide the signal for communications devices such as: radios, television, cell phones

  • Micro waves are used to cook food

  • Infrared waves are used for TV remote controls, night vision


Ultraviolet, X and Gamma Waves

  • Shortest wavelength, highest frequency

  • Cause damage to human cells because wavelength is close to atomic size

  • Ultraviolet – sun bathing

  • X – used to detect bone damage, baggage screening at airports

  • Gamma – radioactive decay


Visible Light

  • Waves that allow us to see color

  • Red – longest wavelength, lowest frequency

    (3.84 x 1014 Hz = 384,000,000,000,000 Hz)

  • Violet – smallest wavelength, highest frequency (7.69 x 1014 Hz = 769,000,000,000,000 Hz)


Light Sources

  • Emit light waves

  • Produce light

  • Sun, light bulbs, flames

    Illuminated Objects

  • Most objects

  • Actually are reflecting light

  • People, plants, rocks, etc.

    Moon – source or illuminated?


Characteristics of Light Waves

  • Intensity (brightness) = amplitude

Large amplitude, a lot of energy (very hot)

Small amplitude, less energy (warm)


Characteristics of Light Waves

  • Color = frequency

    • Order of colors = spectrum

    • Primary colors of light – red, green and blue

      • Red light +green light +blue light = white light

      • Different than pigment colors (ink, paint, etc)

        • These reflect light, they are not sources

          Mixing colors Applet


Light can be reflected or transmitted:

Materials

  • Transparent – transmit clearly (clear glass, still water)

  • Translucent – transmit blurry (frosted glass)

  • Opaque – no transmission (light may be reflected or absorbed)


Speed of light in a vacuum= c

= 299,792,458 m/s

= 2.99792458 x 108 m/s

≈ 3.00 x 108 m/s

Speed of light in any other material depends on optical density (ability of a material to transmit light)

  • Greater optical density, more light slows down

    Airc / 1.003 ≈ 3.00 x 108 m/s

    Water c/1.33

    Diamondc/2.42


Scientific Notation

1. Ex: 300,000,000 → 3.0

0.000345 → 3.45

  • Put a decimal after the first non-zero number and drop any zeroes

  • Determine the power of ten by counting the places before of after the decimal

  • Show the places before or after the decimal using an exponent. Use a negative on your exponent if the decimal is before the number

2. Ex: 300,000,000 → 3.0 8 places after

0.000345 → 3.45

4 places before

  • Ex: 300,000,000 →

  • 3.0 x108

    0.000345 →

    3.45 x 10-4


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