Electromagnetic Spectrum
Objectives
 SWBAT describe the electromagnetic spectrum and
explain the relationship between wavelength, frequency,
speed, and energy.
 SWBAT contrast continuous spectra and atomic emission
spectra and relate these spectra to orbital diagrams.
Essential Question:
 How do we use the theory of electromagnetism by
comparing and contrasting the different parts of the
electromagnetic spectrum in terms of wavelength,
frequency, and energy, and relating them to phenomena
and applications?
Catalyst/Do Now
Rank the following sublevels from highest energy
to lowest energy: 1s, 4s, 2p, 4p, 3s, 3d
2. Like matter, energy cannot be created or destroyed.
Give an example of energy being transferred or
being converted from one form to another.
3. When an electron moves from a higher energy level
to a lower energy level, it loses energy. Where do
you think this energy goes?
1.
Electromagnetic Spectrum
 Electromagnetic radiation is a form of energy that
exhibits wavelike behavior as it travels through
space. Electromagnetic spectrum includes all
forms of electromagnetic radiation.
Electromagnetic Spectrum
 All waves are defined by a characteristic
wavelength and frequency.
 Frequency
(ν) = number of times a wave
cycle passes at point in a given time (Hz or
1/s)
 Wavelength (λ) = distance between the
peaks in a wave
wavelength
Amplitude
Low Energy
Amplitude
wavelength
High Energy
• Waves with longer
wavelengths (larger
waves) have less
energy and lower
frequencies.
• Waves with shorter
wavelengths (smaller
waves) have more
energy and higher
frequencies.
Wavelength, Frequency and Energy
 Waves with longer wavelengths (larger waves) have
less energy and lower frequencies
 Waves with shorter wavelengths (smaller waves)
have more energy and higher frequencies
Relationship between frequency and wavelength
Unknown you want Equation
to solve for
Wavelength (m)
Frequency (Hz)
c
λ=
ν
c
ν=
λ
c = the speed of light = 3 x 108 m/s
What is the wavelength of a radio wave
having the frequency of 5.4 x 1010 Hz?
 Analyze the problem
o Known values: ν = 5.4 x 1010 and c = 3 x 108
o Unknown values: λ
 Solve for the unknown
o If c = λν, then λ = c/ν
o Substitute c and ν into the equation to solve for the
wavelength. The answer should be in units of meters.
What is the wavelength of a radio wave
having the frequency of 5.4 x 1010 Hz?
 Answer:
λ = 3 x 108/ 5.4 x 1010 = 0.0056 = 5.6 x 103
Guided Practice: We do!!
Type of
Wave
Radio
waves
Frequency ν
(Hz or 1/s)
3 x 106
X-rays
λ = c/ν
10-2
Microwaves
Ultraviolet
Wavelength λ Form of the
(m)
equation
used
3 x 1016
10-10
ν = c/λ
Calculate the missing values:
Type of
Wave
Radio
waves
Microwaves
Ultraviolet
X-rays
Frequency ν
(Hz or 1/s)
Wavelength λ Form of the
(m)
equation
used
3 x 106
100
λ = c/ν
3 x 1010
3 x 1016
3 x 1018
10-2
1 x 10-8
10-10
ν = c/λ
λ = c/ν
ν = c/λ
Quantization of Energy
 When electrons move between energy levels, they
give off energy in the form of light. We can use the
following equation to describe this energy:
E = hν
 h = Planck’s constant = 6.626 x 10-34 Js (J = Joule, a
unit of energy)
frequency of 4.0 × 1014 Hz. How much energy
does red light have?
 Analyze the problem
 Known values: ν and h
 Unknown values: E
 Solve for the unknown
 Write the equation: E = hν
 Substitute h and ν into the equation to solve for the energy.
The answer should be in units of Joules.
In the visible spectrum, red light has a
frequency of 4.0 × 1014 Hz. How much
energy does red light have?
 Answer:
E = h x 4 x 1014 = 2.65 x 10-19
frequency of 7.0 x 1014 Hz. How much energy
does violet light have?
 Analyze the problem
 Known values: ν and h
 Unknown values: E
 Solve for the unknown
 Write the equation: E = hν
 Substitute h and ν into the equation to solve for the energy.
The answer should be in units of Joules.
frequency of 7.0 x 1014 Hz. How much energy
does violet light have?
 Answer:
E = h x 7 x 1014 = 4.97 x 10-19
Which would have more energy,
red or violet light?
VIOLET
You Do (15 min)
 Use the relationships to complete the table in your
notes.
Closing
Essential Questions:
How can we understand color and light in terms of
energy?
How is this energy related to electron configurations?