Electromagnetic Spectrum And Light

Electromagnetic Spectrum
And Light
Light and Electrons


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Electrons can be
at different energy
levels: Floors in a
building.
Lowest is called
the Ground State.
Higher states are
Excited States.
Quantum and Photon



A Quantum is the minimum quantity of energy
that can be lost or gained by electrons in an atom
This is because electrons orbit specific quantum
levels around the nucleus of an atom.
A Photon is a particle of electromagnetic radiation
having zero mass and carrying a quantum of
energy
Changing Levels

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If you add the RIGHT amount of energy to an
atom, the electron will jump up energy ‘floors’.
If the electron drops down energy ‘floors’, the
atom gives up the same amount energy in the
form of light.
Nature of Electromagnetic Waves

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Visible light is a small part of the electromagnetic
spectrum.
Electromagnetic radiation has both wave-like and
particle-like properties
All electromagnetic waves travel at the same speed
in a vacuum.

300,000 km/s
Wave Order

From low frequency to high frequency

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TV & FM Radio
Radar/Microwaves
Infrared
Visible Light
Ultraviolet
X-rays
Gamma rays
10 Hz to 106 Hz
109 Hz to 309 Hz
1012 Hz
4 x 1014 to 7 x 1014 Hz
1016 Hz
1019 to 1020 Hz
1024 Hz
C = λf

C = speed of light
•

λ = wavelength (meters)
•

300,000 km per sec
distance between 2 similar points on a wave (ex.
crest to crest)
v = frequency (waves/ sec or Hertz)
•
number of waves that pass a given point in a
specific amount of time
Practice

A certain microwave has a wavelength
of 0.032 meters. Calculate the
frequency of this microwave.
Practice

A certain microwave has a wavelength
of 0.032 meters. Calculate the
frequency of this microwave.
Practice

A wave on a certain guitar string travels
at a speed of 200m/s. Calculate the
wavelength of an “A” note sounding at
440Hz.
Practice

A wave on a certain guitar string travels
at a speed of 200m/s. Calculate the
wavelength of an “A” note sounding at
440Hz.
Energy

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The amount of energy contained in a type of
electromagnetic radiation is directly related to
the frequency: The higher the frequency, the
higher the energy
The amount of energy can be calculated
using Plank’s constant
h = 6.626 x 10-34 Joule•sec
E = hf
Practice

A photon has a frequency () of 2.68 x
106 Hz. Calculate its energy.
Practice


A photon has a frequency () of 2.68 x
106 Hz. Calculate its energy.
E = 1.78 x 10-27 J
Practice

Calculate the energy (E) and
wavelength () of a photon of light
with a frequency () of 6.165 x 1014 Hz.
Practice


Calculate the energy (E) and
wavelength () of a photon of light
with a frequency () of 6.165 x 1014 Hz.
E = 4.1 x 10-19 J
 = 4.87 x 10-7 m
Line Emission Spectrum

Every element has a DIFFERENT finger
print.
Many atoms create light
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Excited electrons, don’t stay excited
forever.
Drop back down to their ground ‘floors’.
Only light of the precise energy
difference between ‘floors’ is given off.
This light goes off in all directions.