the electromagnetic spectrum
DESCRIPTION
The Electromagnetic Spectrum. Rainbows plus a whole lot more. Wave vocabulary. Colors of the rainbow?. Violet Blue Green Yellow Orange Red. Describing light…. Longer wavelength Higher f requency Higher e nergy. Describing light…. Wavelength (nm). - PowerPoint PPT PresentationTRANSCRIPT
The Electromagnetic Spectrum
Rainbows plus a whole lot more
Wav
e vo
cabu
lary
Colors of the rainbow?
Violet Blue Green Yellow Orange Red
Describing light…
Longer wavelength Higher frequency
Higher energy
Describing light…
Wavelength (nm)
More than meets the eye…
Electromagnetic Spectrum
But what is electromagnetic radiation?
• Most waves require a medium.
• EM radiation does not. They can travel in a vacuum
• Gamma rays• X-rays• Ultraviolet• Visible• Infra-red
– “below red”• Microwaves
– Cell phones• Radio waves
High to low energy
Ioni
zing
ra
diat
ion
Ionizing radiation
Glossary Entry
• Subatomic particles or electromagnetic waves energetic enough to detach electrons from atoms or molecules, ionizing the atoms or molecules.
Gamma rays, X-rays, high energy ultraviolet light, alpha particles, and beta particles are examples of ionizing radiation.
Uses for the Electromagnetic Spectrum
Your body emits IR radiation
Try it
Longer wavelength? Higher frequency?
Higher energy?
Spectrum of Electromagnetic Radiation
RegionWavelength Wavelength Frequency Energy(Angstroms) (centimeters) (Hz) (eV)
Radio > 109 > 10 < 3 x 109 < 10-5
Microwave 109 to 106 10 - 0.01 3 x 109 to 3 x 1012 10-5 to 0.01
Infrared 106 to 7000 0.01 to 7 x 10-5 3 x 1012 to 4.3 x 1014 0.01 to 2
Visible 7000 to 4000 7 x 10-5 to 4 x 10-5 4.3 x 1014 to 7.5 x 1014 2 to 3
Ultraviolet 4000 to 10 4 x 10-5 to 10-7 7.5 x 1014 to 3 x 1017 3 to 103
X-Rays 10 to 0.1 10-7 to 10-9 3 x 1017 to 3 x 1019 103 to 105
Gamma Rays < 0.1 < 10-9 > 3 x 1019 > 105
Color Wavelength (nm)
Approximate energy (eV)
Violet 380-450 2.76
Blue 450-495 2.5
Green 495-570 2.2
Yellow 570-590 2.1
Orange 590-620 2.0
Red 620-750 1.65
Energy of the rainbow
Violet Indigo Green Yellow Orange Red
2.76 eV 2.51 eV 2.2 eV 2.1 eV 2.0 eV 1.65 eV
____ Ultraviolet____ X-rays____ Radio waves____ Gamma rays____ Visible____ Infra-red____ Microwaves
Try it
Rank in order of lowest to highest• Frequency• Wavelength• Energy
Energy = Planck’s constant times frequencyE = h•νh = 6.62 x 10-34 Joules•second (J•s)
= 4.13 x 10-15 electron Volt•second (eV•s)ν = frequency in Hertz (cycles/second)
Also rememberc = λ•ν c = speed of light = 3.00 x 108 m/s
So E = h • c / λ
Calculating energy
1. Calculate the energy of a photon of infra-red radiation with a wavelength of 800 nm.
2. Your cell phone emits energy in the microwave region. Calculate the energy of a photon of cell-phone radiation with an wavelength of 10 cm.
3. The energy of a photon is measured as 4x10-19
joules . In what region of the electromagnetic spectrum does it reside? (Hint: calculate in nm)
Try it!!
Vocabulary
Skills– Describe the electromagnetic spectrum using wavelength,
frequency or energy– Rank energies of visible light– Rank energies of electromagnetic spectrum– Convert energy wavelength, frequency energyConcepts– EM radiation does not require a medium
• Can travel in a vacuum– EM radiation travels in packets called photons– Higher energy EM radiation ionizes atoms or molecules
Stuff to know
wavelengthfrequencyionizing radiation
amplitudephoton