# Electromagnetic Waves - PowerPoint PPT Presentation

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## Electromagnetic Waves

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### Electromagnetic Waves A wave transmits energy from the source to the receiver. Electromagnetic waves do this by disturbing the electric and magnetic fields ... – PowerPoint PPT presentation

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Title: Electromagnetic Waves

1
Electromagnetic Waves
• A wave transmits energy from the source to the
• Electromagnetic waves do this by disturbing the
electric and magnetic fields surrounding the
earth.
• The types of electromagnetic waves are arranged
on a spectrum from greatest to smallest frequency.

2
Electromagnetic Spectrum
3
Electromagnetic Spectrum
4
Wave Properties
• Wavelength (?) is the distance between two
successive waves.
• Frequency (f) is the number of waves passing a
point per second.
• V f ? wave speed equation
• Wave speed (v) is the speed of electromagnetic
waves. In a vacuum this is 3.0 x 108 m/s or
186,000 miles per second!

5
Wave Properties
6
Bohr Model of the Atom
• To explain the emission of light, Bohr came up
electrons orbiting around a nucleus.
• This similarity between a planetary model and the
Bohr Model of the atom ultimately arises because
the attractive gravitational force in a solar
system and the attractive Coulomb (electrical)
force between the positively charged nucleus and
the negatively charged electrons in an atom are
mathematically of the same form.

7
Energy Levels of the Atom
energy states by the addition of energy of
certain frequencies
• The excited electron is unstable and falls down
to ground state giving off electromagnetic energy
equal in frequency to the energy change.

8
Hydrogen Emission Series
• The electrons can move to only certain locations
from the nucleus
• The result of this restriction in movement is
specific and distinct wavelengths of EM radiation
is given off as the electrons transition.

9
Energy Quantified
• The energy transitions are quantified and thus
the transitions accept and release only certain
• The energy of each level for the hydrogen atom is
given by the equation
• En RH/n2
• RH is called the Rydberg constant
• RH 2.180 x 10-18 J

10
Energy to Wavelength
• E h f
• h is a constant in nature
• h 6.626 x 10-34 J/Hz
• Rearranging the frequency of absorbed or emitted
light is
• f E h

11
Atomic Spectra
• White light emits all colors because a multitude
of electron transitions occur between energy
levels.
• Spectral Lines give evidence of electron
transitions.
• A specific species of gas emits only a limited
amount of spectral colors because of a more
limited availability of electron transitions.

12
Emission Spectra for H2 and He
13
More Emission Spectra Na, Ne, Hg