The Electromagnetic Spectrum

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Chapter 4

• The Electromagnetic Spectrum
• Part 1

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Demonstration

• Gas spectral tubes
• Neon Argon

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Visible Light

• Part of the Electromagnetic Spectrum

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All types of electromagnetic energy move in waves.

• Light and sound move by waves.
• Light moves at
• 3 x 108 m/s
• Sound moves at
• 340 m/s
• 1 mile 1609 m

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All types of electromagnetic energy move in waves.

• Light moves at
• 3 x 108 m/s
• Sound moves at
• 340 m/s
• Is sound a form of electromagnetic radiation?

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Electromagnetic Waves

• Properties of waves include speed, frequency and
  wavelength
• All electromagnetic waves including light travel
  at a speed of 3 x 108 m/s.

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Wavelength (?)
Measured in units of length m, nm, A
º
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Frequency (?)
Measured in cycles/second hertz (Hz)
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Visible Light
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Why do we want to understand electromagnetic
radiation (light)?

• Well, for one thing, it may someday allow us to
  become invisible.

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Electromagnetic Radiation

• For all waves ? ? c
• c the speed of light 3.00 x 108 m/s

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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?
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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?

• 665 nm 665 x 10-9 m

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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?

• 665 nm 665 x 10-9 m
• c ? ?

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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m

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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz

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A photon of red light has a wavelength of 665 nm.
What is the frequency of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz
• ? 4.51 x 1014/s or Hz

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?
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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?

• 7.25 x 1020 Hz 7.25 x 1020/s

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?

• 7.25 x 1020 Hz 7.25 x 1020/s
• c ? ?

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?

• 7.25 x 1020 Hz 7.25 x 1020/s
• c ? ?
• ? c ? 3.00 x 108 m/s 7.25 x 1020/s

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?

• 7.25 x 1020 Hz 7.25 x 1020/s
• c ? ?
• ? c ? 3.00 x 108 m/s 7.25 x 1020/s
• ? 4.137931 x 10-13 m

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is the wavelength?

• 7.25 x 1020 Hz 7.25 x 1020/s
• c ? ?
• ? c ? 3.00 x 108 m/s 7.25 x 1020/s
• ? 4.137931 x 10-13 m
• ? 4.14 x 10-13 m

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Energy of Electromagnetic Radiation

• For all waves E h ?
• h 6.63 x 10-34 J s or J/Hz

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A photon of red light has a wavelength of 665 nm.
What is the energy of this light?
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A photon of red light has a wavelength of 665 nm.
What is the energy of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz
• ? 4.51 x 1014/s or Hz

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A photon of red light has a wavelength of 665 nm.
What is the energy of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz
• ? 4.51 x 1014/s or Hz
• E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)

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A photon of red light has a wavelength of 665 nm.
What is the energy of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz
• ? 4.51 x 1014/s or Hz
• E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)
• E 2.99013 x 10-19 J

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A photon of red light has a wavelength of 665 nm.
What is the energy of this light?

• 665 nm 665 x 10-9 m
• c ? ?
• ? c ? 3.00 x 108 m/s 665 x 10-9 m
• ? 4.511278 x 1014/s or Hz
• ? 4.51 x 1014/s or Hz
• E h ? (6.63 x 10-34 J s)(4.51 x 1014/s)
• E 2.99013 x 10-19 J 2.99 x 10-19 J

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is its energy?
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An x-ray has a frequency of 7.25 x 1020 Hz. What
is its energy?

• E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is its energy?

• E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)
• E 4.80675 x 10-13 J

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An x-ray has a frequency of 7.25 x 1020 Hz. What
is its energy?

• E h ? (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)
• E 4.80675 x 10-13 J
• E 4.81 x 10-13 J

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wavelength, frequency and energy
Red Light

• ? 665 x 10-9 m
• ? 4.51 x 1014 Hz
• E 2.99 x 10-19 J

• ? 4.14 x 10-13 m
• ? 7.25 x 1020 Hz
• E 4.81 x 10-13 J

X-ray
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Wavelength, frequency and energy

• Wavelength and frequency have an inverse
  relationship.
• Energy and frequency have a direct relationship.
• Electromagnetic radiation with a shorter
  wavelength will have a higher frequency and
  higher energy.
• Electromagnetic radiation with a longer
  wavelength will have a lower frequency and lower
  energy.

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Homework

• Chapter 4 Worksheet 2 (due in two days)