Transcript Electromagnetic Spectrum and Light

Electromagnetic
Spectrum and Light
Chapter 18
Electromagnetic Waves
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Transverse Waves
Consist of constantly changing fields
electric field – space that exerts
electric forces on charged particles
magnetic field – space that
produces magnetic forces
Electromagnetic Waves…
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
Are produced when an electric charge
vibrates or accelerates.
Can travel without a medium. They
can travel through a vacuum, empty
space, or matter.
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!
Use the formula for
Wave Speed…
 to
calculate the varying
wavelengths and frequencies.

Wave speed = wavelength x frequency
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
Photons
•The packets of energy
that make up
electromagnetic radiation
The greater the frequency
the wave has, the more
energy each of its
photons has.
Photoelectric Effect
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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
Intensity
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The rate at which a wave’s 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
Electromagnetic
Spectrum
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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
Parts of the EM Spectrum
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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.
Radio Waves
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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
Infrared Rays
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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
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
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Ultraviolet Rays
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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
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

Gamma Rays
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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
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.
Transparent
 Allows
most of the light to pass
through
 You
can see clearly through it
 Examples:
glass, water
Translucent
 Scatters
it
light that passes through
 You
can see through it, but not
clearly
 Example:
Frosted glass
Opaque
 Absorbs
or reflects all of the
light that strikes it
 You
can’t see through it
 Examples:
Wood, Metal
When light strikes
a medium, it is
either reflected,
absorbed, or
transmitted.
Reflection
An image is formed from waves that
bounce off of a material’s 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.
If light is transmitted it
can be….
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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
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
Prism
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Material that diffracts white light into
a color spectrum of light
Dispersion – process of white light
separating into colors Ex. Rainbow
Primary colors of light
Red
Green
Blue
All 3
together
produce
WHITE light
Secondary colors of light
Yellow
Magenta
Cyan
Any 2 colors of
light that
combine to
produce white
light are
complementary
colors.
Pigments
Material that
absorb some
colors of light
and reflect the
other colors.
 Examples: Paint,
ink, pictures,
and dye

Primary colors of PIGMENTS
All 3 together
produce BLACK
pigment
Yellow Magenta Any 2 pigments
Cyan
that form black
pigments are
complementary
pigments
Sources of Light
1.
Incandescent- Heats a filament
until it glows
Ex. Typical light bulb
Sources of Light
2. Glowing phosphorus – a
phosphor is steadily emitting
photons
Ex. Used in schools,
hospitals, and offices
Sources of Light
3. Laser - Beam of electrons
Sources of Light
4. Neon – electrons move
through a gas inside a glass
tube
Ex. signs
Sources of Light
5. Sodium-vapor Light - Contains
neon and sodium metal
gives off a yellow tint
Ex. Street lights
Sources of Light
6. Tungsten-Halogen Light –
similar to an incandescent light,
but contains halogen gas
Ex. Lamps & headlights