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Electromagnetic waves
Disturbances
that transfer through field
Transverse waves
Can travel through a medium or in
vacuum
at the speed of
light
Produced by
accelerating electrons
Combination of electric and
magnetic fields
that oscillate
perpendicular
to each other and to the direction of the wave
Wave speed, frequency, and wavelength
Related by the equation: v=λf, where v is
wave speed
, f is frequency, and λ is
wavelength
Scientists who contributed to electromagnetic wave theory
Andre Marie Ampere
Michael Faraday
Heinrich Rudolf Hertz
James Clark Maxwell
Hans Christian Oersted
Electromagnetic spectrum
Continuum of electromagnetic waves arranged according to
frequency
and
wavelength
Regions of the electromagnetic spectrum
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Radio waves
Longest
wavelength in the EM spectrum
Produced by
vibrating electrons
in an
antenna
Used to transmit
sound
and
picture
information over long distances
Divided into
wavebands
allocated to specific
radio
services
Low frequency
radio waves
Suitable for
communication
over great distances, but
limited
by earth's curvature
Require
repeaters
to extend range
High frequency radio waves
Can be reflected by the
ionosphere
to transmit over
great distances
Microwaves
Smaller
wavelength
than
radio
waves
Used in satellite communications, radar,
TV
transmission, and
cooking
Satellite communications using microwaves
1.
Microwaves
transmitted by antenna to
satellite
2.
Satellite
amplifies and re-transmits signal to other
antenna
Radar using microwaves
1.
Antenna whirls
to scan area
2. Transmitter sends out
narrow beam
of microwaves in
pulses
3. Distant object
reflects
signal back to
receiver
4.
Direction
and
distance
of object calculated
Terrestrial microwave communications
Used for TV news coverage, cell phones, and microwave ovens
Infrared radiation
Lies beyond the
red
end of
visible
light
Emitted by
all
objects, amount and wavelength depend on
temperature
Detected by infrared cameras and used in
night
vision, remote controls, and
autofocus
cameras
Visible spectrum
Wavelengths of
white light
that the human eye can detect
Ultraviolet
radiation
Shorter
wavelength and
higher
energy than visible light
Used for
sterilization
, detecting forgeries, and producing
vitamin D
rays
Shorter
wavelength and
higher
energy than UV
Penetrate
flesh but not bones, used for
medical imaging
Penetrate
metals
, used for
industrial inspection
Dangerous due to ability to
damage cells
Gamma
rays
Shortest
wavelength
and highest
energy
in EM spectrum
Emitted by
stars
and
radioactive
substances
Can only be blocked by
lead
and
thick concrete
Highly dangerous, used for
cancer treatment
and
sterilization
Angle of incidence
Angle between incident ray and
normal
Angle
of
reflection
Angle
between reflected ray and
normal
Laws of reflection
1.
Angle of incidence
= angle of
reflection
2. Incident ray, normal, and reflected ray lie in the same
plane
Specular reflection
Parallel
incident rays reflect as
parallel
rays
Diffuse reflection
Incident rays are
scattered
in many directions
Reflection
Light bounces off a surface
Refraction
Light
bends as it passes from one
transparent
substance into another