I. Electromagnetic WavesI. Electromagnetic Waves

Waves… a reviewWaves… a review

Most waves are either longitudinal or Most waves are either longitudinal or transverse.transverse.

Sound waves are longitudinal.Sound waves are longitudinal.But *But *all all electromagneticelectromagnetic waves are waves are

transversetransverse……

?

?

1.1. When an electric field changes, so does the When an electric field changes, so does the magnetic field. When one field vibrates—so magnetic field. When one field vibrates—so does the other.does the other.

2.2. RESULT-RESULT- An An electromagneticelectromagnetic

wave.wave.

Click here Click here Animation: Interaction of Animation: Interaction of vibrating chargesvibrating charges

A. Electromagnetic wavesA. Electromagnetic waves1.1. Produced by the movement of electrically Produced by the movement of electrically

charged particlescharged particles

2.2. Can travel in a “vacuum” (they do NOT Can travel in a “vacuum” (they do NOT need a medium)need a medium)

3.3. Travel at the speed of Travel at the speed of

light: 300,000,000 meters/second light: 300,000,000 meters/second (Takes light 8 minutes to move from(Takes light 8 minutes to move from

the sun to earth {150 million miles} the sun to earth {150 million miles}

at this speed.)at this speed.)

(Also known as EM waves)(Also known as EM waves)

Waves of the Electromagnetic SpectrumWaves of the Electromagnetic Spectrum Electromagnetic SpectrumElectromagnetic Spectrum—name for the range of —name for the range of

electromagnetic waves when placed in order of increasing electromagnetic waves when placed in order of increasing frequencyfrequency

Click here Click here ((AnimationAnimation—Size of EMwaves—Size of EMwaves))

RADIO WAVES

MICROWAVES

INFRARED RAYS

VISIBLE LIGHT

ULTRAVIOLET RAYS

X-RAYS

GAMMA RAYS

Wave-particle DualityWave-particle Duality

Light can behave like a wave or like a Light can behave like a wave or like a particleparticle

A “particle” of light is called a A “particle” of light is called a photonphoton

Radio wavesRadio wavesHave the Have the longestlongest wavelengths and wavelengths and

lowest lowest frequencies of all the frequencies of all the electromagnetic waves.electromagnetic waves.

Uses:Uses:TV broadcastingTV broadcastingAM and FM broadcast radio ( each channel is AM and FM broadcast radio ( each channel is

a different frequency)a different frequency)Cell phone communicationCell phone communication

MicrowavesMicrowaves

Wavelengths from 1 mm- 1 mWavelengths from 1 mm- 1 mUses:Uses:

Microwave ovensMicrowave ovensBluetooth headsetsBluetooth headsetsBroadband Wireless InternetBroadband Wireless InternetRadarRadarGPSGPS

How does a microwave oven work?How does a microwave oven work?

Waves transfer energy to the water in the Waves transfer energy to the water in the food causing them to vibrate which in turn food causing them to vibrate which in turn transfers energy in the form of heat to the transfers energy in the form of heat to the food.)food.)

Infrared RadiationInfrared Radiation

Wavelengths in between microwaves and Wavelengths in between microwaves and visible lightvisible light

Uses:Uses:Night vision gogglesNight vision gogglesRemote controlsRemote controlsHeat-seeking missilesHeat-seeking missiles

Visible lightVisible light

Only type of EM wave able to be detected Only type of EM wave able to be detected by the human eyeby the human eye

Violet is the highest frequency lightViolet is the highest frequency lightRed light is the lowest frequency lightRed light is the lowest frequency light

UltravioletUltraviolet

Shorter wavelengths than visible lightShorter wavelengths than visible lightUses:Uses:

Black lightsBlack lightsSterilizing medical equipmentSterilizing medical equipmentWater disinfectionWater disinfectionSecurity images on moneySecurity images on money

Ultraviolet (cont.)Ultraviolet (cont.)

UVAUVA UVB and UVCUVB and UVC

EnergyEnergy Highest of UV Highest of UV waves waves

Lower than UVALower than UVA

Health Health risksrisks

Extremely low Extremely low risk for DNA risk for DNA damagedamage Can destroy Can destroy Vitamin A in skinVitamin A in skin

Can cause DNA Can cause DNA damage, leading to damage, leading to skin cancerskin cancer Responsible for Responsible for sunburnsunburn

X-raysX-rays

Tiny wavelength, high Tiny wavelength, high

energy wavesenergy wavesUses:Uses:

Medical imagingMedical imagingAirport securityAirport security Inspecting industrial weldsInspecting industrial welds

Gamma RaysGamma Rays

Smallest wavelengths, highest energy EM Smallest wavelengths, highest energy EM waveswaves

UsesUsesFood irradiationFood irradiationCancer treatmentCancer treatmentTreating wood flooringTreating wood flooring

Using the EM waves to view the Using the EM waves to view the SunSun

Animation—View a Galaxy at different Animation—View a Galaxy at different wavelengthswavelengths

Brief SUMMARYBrief SUMMARYA. All electromagnetic wavesA. All electromagnetic waves travel at the travel at the

same speed. (300,000,000 meters/second same speed. (300,000,000 meters/second in a vacuum.in a vacuum.

B. They all have different B. They all have different wavelengthwavelength and and different different frequencies.frequencies.Long wavelength-Long wavelength-lowest frequencylowest frequencyShort wavelengthShort wavelength highest frequency highest frequencyThe higher the frequency the The higher the frequency the higher the higher the

energy.energy.