Chapter 13 Lecture - Bbuckner.com

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16 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Chapter 13

Sound

Section 1


Electromagnetic waves


made by vibrating electric charges and can
travel through space.


Electric and magnetic fields


related forces operate even in empty space


Moving electric charge creates magnetic field


Changing magnetic fields create changing
electric fields and vice versa.


Electromagnetic waves


produced when an electric charge is vibrating


Vibrating electric charges are surrounded
by vibrating electric and magnetic fields


Properties of Electromagnetic fields


carry radiant energy


as frequency increases, wavelength decreases


Frequency


number of vibrations per second


measured in hertz


Wavelength


is the distance from one crest to another


measured in meters


Wave speed


the vacuum of space, 300,000 km/s


electromagnetic waves slow as they travel through
matter


Waves and particles


Difference is still not clear



Light can behave as a particle or
wave


Know as duality


Photon


Particle of light whose energy depends
on frequency


All particles can behave like a wave

Section 2


Electromagnetic spectrum


Entire range of electromagnetic wave frequencies


Radio waves


low
-
frequency electromagnetic waves with
wavelengths from less than a cm to about 1000 m


Microwaves


radio wave lengths of about 1 to 10 cm


Radar


radio waves bounced off an object to determine its
speed and location


Magnetic Resonance Imaging (MRI)


radio waves produce an image of inside the body


Infrared waves


slightly higher frequency than radio waves


people feel it as thermal energy or warmth


Visible light


wavelengths between ~390 to 770 billionth of a meter


can be seen with the eye


Ultraviolet waves


Have frequencies slightly higher than visible light; can
damage skin


Ultraviolet light


can kill bacteria


can be absorbed by some fluorescent materials and released
as visible light


Ozone layer


absorbs most of the Sun’s harmful ultraviolet waves.


X rays
and
gamma rays


ultra
-
high
-
frequency electromagnetic
waves that can travel through matter,
break molecular bonds & damage cells


X rays


used to provide images of bones and to
examine suitcases at airports without
opening them.


Radiation therapy


used to kill diseased cells

Section 3


Radio transmission


radio converts electromagnetic waves into sound
waves


Carrier wave


specific frequency which radio station is assigned


AM radio


broadcast by varying amplitude of carrier wave


frequencies range from 540 to 1,600 thousand
vibrations per second


FM radio


transmit by varying frequency of carrier wave


frequencies range from 88 million to 108 million
vibrations per second


Television


sounds and images changed into electronic
signals broadcast by carrier waves



Audio


sent by FM radio waves


Video


sent by AM signals


Cathode
-
ray tube


A sealed vacuum chamber with a coated
screen that receives electron beams to
provide images


Telephones


microphone converts sound waves into
electrical signal


Cell phone


electrical signal creates a radio wave that is
transmitted to and from a microwave tower


Cordless phone


transceiver

sends one radio signal & receives
another at different frequency from base unit


Pagers


radio receiver on which a message is left


Communication satellites


high frequency microwave signal is transmitted to a
satellite


satellite amplifies it and returns it to Earth at a
different frequency


Satellite telephone systems


mobile phones transmit radio signals to a satellite


satellite relays them back to a ground station that
passes the call into the telephone network


Television satellites


uses microwaves rather than longer
-
wavelength
radio wave


ground receiver dish focuses the microwave beam
onto an antenna


Global positioning system


system of satellites, ground stations,
and receivers that provide
information about the receiver’s
location on or above the Earth’s
surface


G.P.S.