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.