Chapter 13 Lecture -

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16 Νοε 2013 (πριν από 4 χρόνια και 5 μήνες)

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Chapter 13


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


number of vibrations per second

measured in hertz


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

Waves and particles

Difference is still not clear

Light can behave as a particle or

Know as duality


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

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


radio wave lengths of about 1 to 10 cm


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
gamma rays

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

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


sounds and images changed into electronic
signals broadcast by carrier waves


sent by FM radio waves


sent by AM signals

ray tube

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


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


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


radio receiver on which a message is left

Communication satellites

high frequency microwave signal is transmitted to a

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
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