Unit 5: Energy and Light
Name: _________________________________
Unit 5- Light and Energy
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Description
Warm-up
Electromagnetic Spectrum Notes
Light and Energy Notes
Light and Energy Worksheet
Flame Test PreLab
Flame Test Lab
Light and Energy Calculation
Notes
Wavelength and Frequency
Energy
Gas Tubes Prelab
Gas Tubes Lab
Unit 5 Online Review
Unit 5 Quiz Review
5
Unit 5 Quiz
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Due Date
Completed
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Thursday, November 17th and Friday, November 18th
Unit 5: Energy and Light
Warm-up
Day 2
1. What color of visible light has the lowest frequency?
2. What has the shortest wavelength: x-rays or UV light?
3. What has the highest energy: microwave or radiowave?
Day 3
1. What is the frequency of light with a wavelength of 2.38x10-3 µm?
2. What is the wavelength of light with an energy of 420. kJ?
Day 4
1. Draw Bohr’s model of the atom.
2. What is the speed of light?
3. What is Planck’s constant?
Day 5:
1. Calculate the wavelength emitted if the frequency of radiation is 5.09 x1014
Hz? What color would this light be?
Unit 5: Energy and Light
Electromagnetic Spectrum Notes
_______________________ is a form of energy that emits wave-like behavior as
it travels through space.
Amplitude (a)-
Wavelength (λ)-
Frequency (ν)Which of the following has a higher frequency?
Electromagnetic radiation can be displayed in the ______________________.
This spectrum places all of the wave types in order based on wavelength (λ) and
frequency (ν).
Unit 5: Energy and Light
Light and Energy Notes
In 1900 ____________________ helped us move toward a better understanding
of _____________________.
Matter can gain or lose ___________ only in small, specific amounts called
__________.
A _____________________ is the __________________ amount of energy that
can be gained or lost by an atom.
Light and energy can't always be explained using waves.
In 1905 Albert Einstein proposed that electromagnetic radiation has both
________________and ___________________ like natures.
In the photoelectric effect electrons (or photoelectrons) are emitted from a
metal's surface when light or energy of a specific_________________ comes in
contact with the metal.
While a beam of light has many _________________ characteristics, the beam
can also be thought of as a stream of tiny _________________ or bundles of
energy called photons.
A ____________________ is a particle of electromagnetic ______________ with
no______________that carries a quantum of energy.
Louis de Broglie (1892 - 1987)
o Only ________________numbers of wavelengths are allowed in a circular
orbit of a fixed radius
o Light has characteristics of both _______________ and ________________
o Electrons move in ______________ motion with restricted circular orbits
Neils Bohr (1885 - 1962)
o Proposed a _____________________
o Predicted frequencies of hydrogen's atomic _______________________
o Atoms have only certain _____________________________
o Related energy states to the motion of electrons in circular orbits
Unit 5: Energy and Light
By passing light through an elemental gas:
1. the atoms ____________ energy
2. an electron will move to a __________ energy level.The atom is then said to be in an
_________________state
3) This energy is then released in the form of ___________ when the
electron falls back to the ____________ state.
The ________________ the electron has to fall, the more energy is
released and the _________ the wavelength of light is emitted.
A prism will separate the light into an atomic emission spectrum
Emission Spectrum: series of ___________ which correspond to a
series of ______________ of the _________________ waves
emitted by that element.
Unit 5: Energy and Light
Light and Energy Worksheet
Answer all questions in complete sentences.
1. Define photon.
2. According to deBroglie, how do electrons move?
3. Draw a picture of Bohr’s atomic model. Label n = 1 – n = 4 and indicate the
ground state.
4. What colors are present in white light?
5. List the colors of the visible spectrum in order of increasing energy. The
photons of which type of visible light would carry the greatest frequency?
6. What type of visible light has more energy, blue light or orange light?
7. Which type of electromagnetic radiation would be more harmful to humans:
microwaves or gamma rays? Explain.
8. Put the following in order from lowest frequency to highest frequency: UV
light, Radio waves, infrared and visible light.
Unit 5: Energy and Light
9. Which form of electromagnetic radiation would reach Earth faster if both
forms were emitted simultaneously from a probe in space: X-rays or gamma rays?
Explain.
10. Which photons would have a greater amount of energy: a photons with a
wavelength of 125 nm or a wavelength of 3456 pm?
11. Draw a wave and label it with the three characteristic properties of all waves
and explain what is meant by each. What units are used to measure λ and ν?
12. Explain the relationship between the frequency and wavelength of a photon.
13. Radio stations can broadcast in an AM frequency or an FM frequency. A
popular AM station in Washington is broadcast at 980 kHz (it broadcasts Redskins
games) and a popular FM station broadcasts at 97.1 MHz. Which ration station
broadcasts with a longer wavelength?
14. Explain what is meant by a quantum of energy.
15. UV – A and UV – B rays will give you a sunburn. If the wavelength emitted by
a photon classified as UV-A light is 380 nm and the wavelength emitted by a
photon is classified as UV-B is 313 nm, which rays are responsible for the worse
sunburn? Explain.
Unit 5: Energy and Light
Flame Tests Lab
Introduction
According to the Bohr theory of the atom, electrons may occupy only specific energy
levels. When an atom absorbs sufficient energy, and electron can “jump” to a higher energy
level. Higher energy levels tend to be less stable, however, and if a lower energy level is
available, the electron will “fall” back, giving off energy in the process. The difference in
energies between the two levels is emitted in the form of a photon of electromagnetic
’s
between 400 and 700 nm, the energy is emitted as visible light. The color of the light depends
on the specific energy change that is taking place.
White light is a continuous spectrum in which all wavelengths of visible light are
present. An excited atom, however, produces one or more specific lines in its spectrum,
corresponding to the specific changes in energy levels of its electrons. Because each element
has a distinct electron configuration, each has a unique line spectrum.
Flame tests are a quick method of producing the characteristic colors of metallic ions.
The loosely-held electrons of a metal are easily excited in the flame of a lab burner. The
emission of energy in the visible portion of the spectrum as those electrons return to lower
energy levels produces a colored flame. The color is a combination of the wavelengths of each
transition, and may be used to determine the identity of the ion.
In this investigation you will perform flame tests on seven metallic ions, then use your
results to determine the identity of several unknowns.
Pre-Lab Questions
1.
What does a flame test indicate about the energy changes taking place among the
electrons in a metallic ion?
2.
What wavelengths correspond to the visible spectrum? Which color has the
shortest wavelength? The longest?
3.
Look up the MSDS for the chemical in the observations section that corresponds
with your group number (Group 1 look up LiCl, Group 2 look up NaCl, etc). List the
possible hazards of working with this chemical.
Unit 5: Energy and Light
Procedure:
1. Light the Bunsen burner. (This process will be demonstrated at the beginning of the lab.)
2. While AT LEAST one member of your lab group stays with the Bunsen burner, take the
crucible tongs to the fume hood and retrieve a q-tip soaked in one of the metals above
(make note of which chemical you are doing).
3. Put the q-tip in the Bunsen burner and record the color of the flame in the data table.
4. Place discarded q-tips in a beaker to be disposed of at the end of the lab.
5. WASH THE CRUCIBLE TONGS!!!
6. Repeat for all remaining metals and the two unknowns.
Observations:
1. LiCl
5. CaCl2
2. NaCl
6. SrCl2
3. KCl
7. CuCl2
4. BaCl2
Analysis and Conclusions:
1. Identify the two metals in each of the unknown solutions and explain the reasoning for
the identification.
2. Place the known metal ions in order from highest to lowest energy emitted.
3. Compare the energies of the wavelengths emitted for lithium, sodium and potassium.
How does the energy emitted relate to the metal’s position on the periodic table?
Explain.
4. Is the Bohr model of the atom the most current model? Explain.
Unit 5: Energy and Light
Light and Energy Calculation Notes
All electromagnetic waves travel at the same speed in a _______________.
This speed _________ is _______________ in a vacuum.
o c is more commonly referred to as the ________________________.
_________________
c = speed of light, 3.00*108 m/s
λ = ______________
ν = ______________
What is the frequency of light with a wavelength of 380. nm?
What is the wavelength of light with a frequency of 98.6 kHz?
________________
E = ____________
h = Planck's Constant, 6.626*10-34 Js
ν = ____________
What is the energy of light with a frequency of 1430 MHz?
What is the frequency of light with an energy of 3.40*10-19 J?
Unit 5: Energy and Light
Wavelength and Frequency
1. What is the wavelength of a photon with a frequency of 4.5 x 10 16 Hz.
2. What is the wavelength associated with a frequency of the radio station
91.9MHz?
3 A laser used in eye surgery to fuse detached retinas produces radiation with a
frequency of 4.69 x 1014 Hz. What is the wavelength associated with this
frequency?
4. What is the frequency of light with a wavelength of 360nm?
5. What is the frequency of light with a wavelength of 2.32 pm?
Unit 5: Energy and Light
Energy
1. What is the energy associated with light that has a frequency of 97.1 kHz?
2. Calculate the frequency of a photon with an energy of 2.3 x 10 -22J.
3 A laser used in eye surgery to fuse detached retinas produces radiation with a
frequency of 4.69 x 1014 Hz. What is the energy associated with this frequency?
4. What is the energy associated with light with a wavelength of 457nm?
5. What is the energy of a photon with a wavelength of 345 nm?
6. Calculate the wavelength of light with an energy of 4.42*10 -19 J. What color is
this light?
Unit 5: Energy and Light
Unit 5 Quiz Review
You must memorize Speed of Light AND Planck’s Constant.
1. For each pair, determine which has the lowest energy, highest frequency, and
longest wavelength.
X-ray / Microwave
Orange light / Violet light Radiowaves /Gamma
Rays
Low Energy:
Low Energy:
Low Energy:
High ν:
High ν:
High ν:
Long λ:
Long λ:
Long λ:
2. Draw a picture of the Bohr model, label the ground state and give the major
failing of the model, then explain what happens within an atom when we see light
being emitted.
3. List the electromagnetic spectrum in order of decreasing energy.
4. Discuss the contributions of Neils Bohr.
5. Discuss the contributions of Max Planck.
6. Discuss the contributions of Louis deBroglie.
7. Define photon.
8. Indicate which of the following drops would release ultraviolet light and why.
n=2→n=1
n=4→n=2
n=6→n=4
Unit 5: Energy and Light
Calculations:
9. What is the frequency of light with a wavelength of 5.7*10 -7 m?
10. What is the wavelength of a radiowave with a frequency of 87.9 MHz?
11. What is the energy of a photon with a frequency of 53.2 kHz?
12. What is the frequency of a photon with an energy of 6.39*10 -15 J?
13. What is the energy of a photon with a wavelength of 7.53 pm?
14. What is the energy of a photon with a wavelength of 345 nm?
15. A laser used in eye surgery to fuse detached retinas produces radiation with a
frequency of 4.69 x 1014 Hz. What is the wavelength associated with this
frequency?
16. What is the energy associated with the frequency in problem 15?
17. Calculate the energy associated with yellow light with a wavelength of
589nm.