Electromagnetic Waves

Electromagnetic Waves

• Electromagnetic Waves– Made by vibrating

electric charges– Can travel through space

where matter is not present

– We cannot hear them, but can feel and experience their effects

• Vibrations of Electric Charges

Electromagnetic Waves

• Electromagnetic Waves– Travel by transferring

energy between vibrating electric and magnetic fields

– Like some mechanical waves, electromagnetic waves are considered transverse

Electric and Magnetic Fields

• Electric Fields– Electric field surrounds

all electric charges– Electric Field Lines

• Magnetic Fields– Magnetic field surrounds

all magnets– Magnetic Field Lines

Electric and Magnetic Fields

Making Electromagnetic Waves

• Electric charges vibrate• Electric field around it

changes• The magnetic field

around the charge changes

• Both fields change continuously creating the wave

Making Electromagnetic Waves

• Electromagnetic Waves

• Making of Electromagnetic Wave

Properties of Electromagnetic Waves

• All objects contain charged particles

• All objects emit electromagnetic waves

• Radiant Energy– Energy carried by EM

waves

Properties of Electromagnetic Waves

• Wave speed– Travel at 300,000 km/s

in the vacuum of space– Called “speed of light”– Usually travel slowest in

solids– Travel fastest in gases

Properties of Electromagnetic Waves

• Wavelength and Frequency– Crest to crest– As frequency increases,

wavelength decreases

Waves and Particles• Em waves– Can behave like particles– This is why energy depends

on frequency, not amplitude

• Photons– Particles of

electromagnetic waves– Carrier of electromagnetic

radiation

Electromagnetic Spectrum

• Frequency range– Wide variety of

frequencies– Entire range is known as

the electromagnetic spectrum

Radio Waves

• Lowest frequency on the spectrum

• Can’t see or hear• Functions:– Carry radio waves– Used by some cell phone

towers– RADARs (Radio

Detecting and Ranging)– MRIs

Microwaves

• Little shorter wavelengths than radio waves

• Functions– Cell phone towers– Satellite signals– Microwave ovens

Infrared Waves

• Shorter wavelengths than radio or microwaves

• Functions– Transmits thermal

energy– Remote controls– CD-ROMs are read by

infrared waves– Infrared imagery

Visible Light

• Only part of the spectrum we can see

• ROY G BIV

Ultraviolet Waves

• Can enter skin cells• Overexposure can cause

skin damage and cancer• UVA and UVB waves• Functions

– Kills bacteria on objects such as food or medical supplies

– Make some materials fluoresce (CSI)

X-Rays

• Can penetrate skin• Functions– X-rays of bones and

teeth– At airport to screen

luggage and other devices

Gamma Rays

• Shortest wavelength of the spectrum

• Functions– Radiation therapy in

which gamma rays kill diseased or cancerous cells

Radio Communication

• Radio Transmission– Each station assigned a

certain frequency– Carrier Wave

• Specific frequency of the electromagnetic wave assigned to a station

AM Radio

• AM Radio– AM = amplitude

modulation– Broadcasts by varying

the amplitude of the carrier wave

– AM carrier range from frequencies of 540,000 to 1,600,000 HZ

FM Radio

• FM Radio– FM = Frequency

Modulation– FM broadcasts by

changing the frequency of the carrier wave

– Frequencies range from 88 million to 108 million Hz