Electromagnetic Spectrum. Range of Behavior Electromagnetic waves are characterized by their...
-
Upload
jocelyn-stanley -
Category
Documents
-
view
217 -
download
0
Transcript of Electromagnetic Spectrum. Range of Behavior Electromagnetic waves are characterized by their...
Electromagnetic Electromagnetic SpectrumSpectrum
Range of BehaviorRange of Behavior Electromagnetic waves are Electromagnetic waves are
characterized by their characterized by their wavelength or frequency.wavelength or frequency.• Linked by the speed of lightLinked by the speed of light
The frequency is associated The frequency is associated with an energy.with an energy.• High frequency is high energyHigh frequency is high energy
The common unit is the The common unit is the electron-volt (eV).electron-volt (eV).• Work done by 1 V potential on Work done by 1 V potential on
one electronone electron
hc = 1.240 keV nm
c
hchE
Electromagnetic RadiationElectromagnetic Radiation
Traditional upper boundaries for types of EM radiation:Traditional upper boundaries for types of EM radiation:
(m)(m) (Hz)(Hz) E E (eV)(eV) Radio waves Radio waves 11 33101088 1.241.241010-6-6
MicrowavesMicrowaves 111010-3-3 3310101111 1.241.241010--
33
InfraredInfrared 0.750.751010-6-6 4410101414
1.651.65 Visible lightVisible light 0.40.41010-6-6 7.57.510101414 3.13.1 Ultraviolet lightUltraviolet light 1.21.21010-8-8 2.42.410101616 11101022
X-raysX-rays 1.41.41010-11-11 3310101919 1.21.2101055
Gamma rays Gamma rays (highest energy)(highest energy)
Radio WavesRadio Waves Radio waves primarily come Radio waves primarily come
from the oscillation of currents from the oscillation of currents in conductors.in conductors.
A 1 MHz frequency has an A 1 MHz frequency has an energy of 6.6 x 10energy of 6.6 x 10-28-28 J. J.
The long wavelengths travel The long wavelengths travel easily and are not interfered by easily and are not interfered by atoms.atoms.• Except conductorsExcept conductors
MicrowavesMicrowaves Microwaves are very short Microwaves are very short
wavelength radio waves.wavelength radio waves.
Microwaves are associated Microwaves are associated with the vibrations of some with the vibrations of some atoms and molecules.atoms and molecules.
Water molecules act as a Water molecules act as a dipole.dipole.• Motion increased by Motion increased by
microwavesmicrowaves
• Causes heating Causes heating
Radiation from HeatRadiation from Heat Heated objects give off Heated objects give off
electromagnetic waves.electromagnetic waves.• Higher temperature has more Higher temperature has more
radiationradiation
A hot object gives off a A hot object gives off a spectrum of frequencies.spectrum of frequencies.• Shifts based on temperatureShifts based on temperature
This is called blackbody This is called blackbody radiationradiation
low energy
high energy
frequency
intensity
InfraredInfrared Molecules are heated by Molecules are heated by
infrared waves.infrared waves.• Radiant heatRadiant heat
Wavelengths longer than Wavelengths longer than visible light are called infrared visible light are called infrared rays.rays.• Come from warm objectsCome from warm objects
Visible LightVisible Light Visible light is radiation in a Visible light is radiation in a
narrow band of wavelength.narrow band of wavelength.• 400 nm to 800 nm400 nm to 800 nm
• Narrower ranges are colorsNarrower ranges are colors
Corresponds to maximum Corresponds to maximum output from the Sun.output from the Sun.
Many atoms and molecules Many atoms and molecules have specific behavior at have specific behavior at unique frequencies of light.unique frequencies of light.
low energy
high energy
frequency
intensity
UltravioletUltraviolet Ultraviolet rays have shorter Ultraviolet rays have shorter
wavelengths than visible light.wavelengths than visible light.• Higher energyHigher energy
• Often with visible lightOften with visible light
Some molecules absorb Some molecules absorb ultraviolet and reemit visible ultraviolet and reemit visible light.light.• Fluorescent lightFluorescent light
X-RaysX-Rays X-rays are associated with X-rays are associated with
energetic transitions in atoms.energetic transitions in atoms.
Continuous spectra result from Continuous spectra result from electron bombardment.electron bombardment.
The short wavelength x-rays The short wavelength x-rays can penetrate materials.can penetrate materials.• Stopped by dense atomsStopped by dense atoms
target
electrons
x-ray
Gamma RaysGamma Rays Gamma rays are photons Gamma rays are photons
associated with nuclear or associated with nuclear or particle processes.particle processes.• Energy range overlaps: soft Energy range overlaps: soft
gamma equals hard x-raygamma equals hard x-ray
Acceleration of a very Acceleration of a very energetic charged particle energetic charged particle gives x-rays and gamma rays.gives x-rays and gamma rays.• Called bremsstrahlungCalled bremsstrahlung
next
e
e
Z