Chapter 5 Sec. 1: Light and Quantized Energy NOTES
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To understand how the arrangement of the electrons in an atom relates to its chemical
properties you must understand the nature of light
Light has a dual nature – it acts like a wave and also like a particle
Wave Nature of Light
o Electromagnetic radiation:
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Examples of electromagnetic radiation:
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All electromagnetic waves travel at the speed of 3.00 x 108 m/s in a vacuum which
is denoted by the symbol c.
 c = speed of light = 3.00 x 108 m/s
o 3 Main Characteristics of a Wave
 1) Wavelength (lambda, λ)
 Characteristics of wavelength:
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2) Frequency (nu, ν)
 Characteristics of frequency:
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3) Amplitude
 Characteristics of amplitude:
o Speed, Frequency, and Wavelength Equation:
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c=
λ=
ν=
With this equation frequency and wavelength are inversely related to each other
meaning that as one increases the other will decrease.
Question #1: As the frequency of a wave decreases will the wavelength decrease,
stay the same, or increase?
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Question #2: As the wavelength of a wave increases will the frequency decrease,
stay the same, or increase?
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Example #1: The wavelength of the radiation which produces the yellow color of a
sodium vapor light is 589.0 nm. What is the frequency of this radiation?
 Remember: c = λν
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Example #2: A wave has a frequency of 559 Hz. What is the wavelength of the
radiation?
 Remember: c = λν
o Electromagnetic Spectrum
 When white light passes through a prism it separates into a continuous spectrum
of colors with each point on the spectrum having a specific wavelength and
frequency.
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The visible light you see only makes up a small portion of what we call the
Electromagnetic Spectrum or the EM spectrum which includes all forms of
electromagnetic radiation.
 The EM spectrum shows us the wavelengths, frequencies, and energies of the
different types of electromagnetic radiation.
 For the visible light range remember:___________________________________ to
remember the order of the colors.
 IMPORTANT TO REMEMBER: Violet light has the highest energy, the
highest frequency, and the shortest wavelength while red light has the
lowest energy, the lowest frequency, and the longest wavelength.
Particle Nature of Light
o In 1900, the German physicist Max Planck started studying the light emitted by heated
objects and found that matter can gain or lose energy only in small, specific amounts
called quanta.
 Quantum:
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Energy of a Quantum Equation:
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Equantum =
h=
ν=
This equation shows that as the frequency increases the energy will also
increase and vice versa.
o Photoelectric Effect:
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Trends: (1) When the intensity of the light increases, the number of electrons
ejected increases, and (2) when the frequency or energy of the light increases, the
energy of the ejected electrons increases.
Light’s Dual Nature
o In 1905 Albert Einstein proposed that light had a dual nature and that a beam of light
could be thought of as a beam of bundles of energy called photons
 Photon:
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Energy of a Photon Equation:
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 Ephoton =
 h=
 ν=
Ex #1) What is the energy of a photon that has a frequency of 5.090 x 10 14 Hz?
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Ex #2) The energy of a photon is 2.676 x 10-20 J. What is the frequency of that
photon?
Atomic Emission Spectra
o Unique to each element
o Is the set of wavelengths of the electromagnetic waves emitted by electrons dropping to
lower energy levels and giving off energy.
o Note that the atomic emission spectra are not continuous but that there are specific lines
of color – this is because there are only certain energy levels that electrons can jump
between.
o QUESTION: In your own words, how is light produced?