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Electromagnetic Spectrum and Light

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Title: Electromagnetic Spectrum and Light


1
Electromagnetic Spectrum and Light
  • Chapter 18

2
Electromagnetic Waves
  • Transverse Waves
  • Consist of constantly changing fields
  • electric field space that exerts electric
    forces on charged particles
  • magnetic field space that produces magnetic
    forces

3
Electromagnetic Waves
  • Are produced when an electric charge vibrates or
    accelerates.
  • Can travel without a medium. They can travel
    through a vacuum, empty space, or matter.

4
Speed of Light
  • In a vacuum, the speed of light is 3.00 x 108
    m/s.
  • All electromagnetic waves will travel at this
    speed in a vacuum, but they will differ in
    wavelength and frequency!

5
Use the formula for Wave Speed
  • to calculate the varying wavelengths and
    frequencies.
  • Wave speed wavelength x frequency

6
Is electromagnetic radiation a wave of a particle?
  • Travels like a wave with interference
  • Travels in a straight line and casts shadows like
    a particle

7
Photons
  • The packets of energy that make up
    electromagnetic radiationThe greater the
    frequency the wave has, the more energy each of
    its photons has.

8
Photoelectric Effect
  • Blue light has a higher frequency than red light,
    so blue light photons have more energy.
  • Blue light has photons that have enough energy to
    cause electrons to be emitted from a metal
    surface
  • The emission of electrons from the metal surface
    is the photoelectric effect

9
Intensity
  • The rate at which a waves energy flows through a
    given unit of area
  • Brightness of the light
  • The intensity of light decreases as photons
    travel farther from the source of the light.
  • Example Spray Paint

10
Electromagnetic Spectrum
  • Shows the frequencies of electromagnetic
    radiation increasing from left to right
  • The spectrum goes from red to violet anything
    beyond the red band is called infrared radiation

11
Parts of the EM Spectrum
  • Visible light is the only part that of the
    spectrum that you can see.
  • The parts of the spectrum include radio waves,
    infrared waves, visible light, ultraviolet rays,
    x-rays, and gamma rays.

12
Radio Waves
  • Used in radio, tv, microwave ovens, and radars
  • Longest wavelength and lowest frequency
  • Amplitude modulation (AM) the amplitude of the
    wave is varied
  • Frequency modulation (FM) the
  • frequency of the wave is varied

13
Infrared Rays
  • Have higher frequencies than radio waves, but
    lower than red light
  • Used as a source of heat (restaurants and zoos)
  • Thermographs color-coded
  • pictures that show variations in temperature

14
Visible Light
  • The light that you can see with the human eye
  • Each wavelength in the visible spectrum
    corresponds with a frequency and has a particular
    color.
  • ROY G BIV

15
Ultraviolet Rays
  • Has a higher frequency than violet light
  • Used in medicine and agriculture
  • Moderate exposure helps your skin produce vitamin
    D
  • Used to kill microorganisms
  • and help plants grow in a
  • nursery during winter

16
X-Rays
  • Used in medicine, industry, and transportation to
    make pictures of the inside of solid objects
  • Too much exposure can kill or damage the living
    tissue

17
Gamma Rays
  • Have the shortest wavelength and the highest
    frequency
  • Have the most energy and the greatest penetrating
    ability
  • used in the medical field to kill cancer cells
    and make pictures of the brain
  • Also used in industry as
  • inspection tools

18
Without Light Nothing is Visible.
  • When you look at objects, what you are seeing is
    light.
  • The behavior of light is affected by the material
    that it strikes.

19
Transparent
  • Allows most of the light to pass through
  • You can see clearly through it
  • Examples glass, water

20
Translucent
  • Scatters light that passes through it
  • You can see through it, but not clearly
  • Example Frosted glass

21
Opaque
  • Absorbs or reflects all of the light that strikes
    it
  • You cant see through it
  • Examples Wood, Metal

22
When light strikes a medium, it is either
reflected, absorbed, or transmitted.
23
Reflection
  • An image is formed from waves that bounce off of
    a materials surface
  • 1. Regular Reflection Image formed is clearly
    defined looks exactly like the object.
  • Example mirror
  • 2. Diffuse Reflection Light scatters in many
    different directions due to an irregular surface.

24
If light is transmitted it can be.
  • Refracted Bending of light from one medium to
    another Ex straw in a cup
  • mirage false or distorted image
  • Polarized consists of 2 filters that block
    horizontal and vertical waves.
  • Ex. Sunglasses use a
  • vertical filter to block
  • horizontal light

25
If light is transmitted it can be.
  • Scattered light is redirected
  • when it passes through a medium
  • Ex Sunrise and Sunset red and orange light is
    what
  • makes it to your eyes

26
Prism
  • Material that diffracts white light into a color
    spectrum of light
  • Dispersion process of white light separating
    into colors Ex. Rainbow

27
Primary colors of light
Red
All 3 together produce WHITE light
Blue
Green
28
Secondary colors of light
Any 2 colors of light that combine to produce
white light are complementary colors.
Magenta
Yellow
Cyan
29
Pigments
  • Material that absorb some colors of light and
    reflect the other colors.
  • Examples Paint, ink, pictures, and dye

30
Primary colors of PIGMENTS
All 3 together produce BLACK pigment Any 2
pigments that form black pigments are
complementary pigments
Magenta
Yellow
Cyan
31
Sources of Light
  • Incandescent- Heats a filament until it glows
  • Ex. Typical light bulb

32
Sources of Light
  • 2. Glowing phosphorus a phosphor is steadily
    emitting photons
  • Ex. Used in schools,
  • hospitals, and offices

33
Sources of Light
  • 3. Laser - Beam of electrons

34
Sources of Light
  • 4. Neon electrons move through a gas inside a
    glass tube
  • Ex. signs

35
Sources of Light
  • 5. Sodium-vapor Light - Contains neon and sodium
    metal
  • gives off a yellow tint
  • Ex. Street lights

36
Sources of Light
  • 6. Tungsten-Halogen Light similar to an
    incandescent light, but contains halogen gas
  • Ex. Lamps headlights
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