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 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 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 Photons 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