The Photoelectric Effect
Teacher Vanessa Baker
Subject Area(s) Physical Science
Associated Unit: 25
Lesson Title: Using the Photoelectric Effect to Demonstrate the Particle Nature of Light
Grade Level
Lesson #
7 (6-8)
Figure: 1
(https://upload.wikimedia.org/wikipedia/commons/7/77/Photoelectric_effect.png)
1 of 1
ADA Description: Photoelectric Effect
Caption: Energy from photons absorbed and used to liberate electrons from atomic binding
Lesson Dependency : None
Group size: Groups of 4
Time Required: 1hr
Summary
Using the Photoelectric Effect students will learn about the nature particles of lights. This effect explains
that when light is directed on a metal, electrons are released from its surface. In which, the kinetic flow
of particles will create an electric current. The intensity of light will determine the productivity of light.
Engineering Connection
Photoelectric Effect Apparatus is designed very specifically to measure the current of photoelectrons.
Students will construct a model of the Photoelectric Effect represented by an electroscope.
Engineering Category =
Choose the category that best describes this lesson’s amount/depth of engineering content:
1. Relating science and/or math concept(s) to engineering
2. Engineering analysis or partial design
3. Engineering design process
Keywords
Angle, light, photons, electrons, photoelectric effect, electric current, intensity
Educational Standards (List 2-4)
1
NGSSS Standard
Big Idea 10: Forms of Energy
SC.7.P.10.1: Illustrate that the sun's energy arrives as radiation with a wide range of wavelengths,
including infrared, visible, and ultraviolet, and that white light is made up of a spectrum of many different
colors.
SC.7.P.10.2 Observe and explain that light can be reflected, refracted, and/or absorbed. Assessed as
SC.7.P.10.3 Recognize that light waves, sound waves, and other waves move at different speeds in
different materials. (Cognitive Complexity: Level 3: Strategic Thinking & Complex Reasoning)
ITEEA Standard
Standard 9. Students will develop an understanding of engineering design.
Grades (6-8)
F. Design involves a set of steps, which can be performed in different sequences and
repeated as needed.
G. Brainstorming is a group problem-solving design process in which each person in the
group presents his or her ideas in an open forum.
H. Modeling, testing, evaluating, and modifying are used to transform ideas into practical
solutions.
NGSS Standard
MS-PS4-2. Develop and use a model to describe that waves are reflected, absorbed, or transmitted
through various
materials. [Clarification Statement: Emphasis is on both light and mechanical waves. Examples of models
could include drawings, simulations, and written
descriptions.] [Assessment Boundary: Assessment is limited to qualitative applications pertaining to light
and mechanical waves.]
MS-PS4-3. Integrate qualitative scientific and technical information to support the claim that digitized
signals are a more
FL Standard
LAFS.7.RI.3.7
Compare and contrast a text to an audio, video, or multimedia version of the text, analyzing each
medium’s portrayal of the subject (e.g., how the delivery of a speech affects the impact of the words).
Cognitive Complexity: Level 2: Basic Application of Skills & Concepts
LAFS.7.SL.1.1
Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with
diverse partners on grade 7 topics, texts, and issues, building on others’ ideas and expressing their own
clearly.
a. Come to discussions prepared, having read or researched material under study; explicitly draw on that
preparation by referring to evidence on the topic, text, or issue to probe and reflect on ideas under
discussion.
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b. Follow rules for collegial discussions, track progress toward specific goals and deadlines, and define
individual roles as needed.
c. Pose questions that elicit elaboration and respond to others’ questions and comments with relevant
observations and ideas that bring the discussion back on topic as needed.
d. Acknowledge new information expressed by others and, when warranted, modify their own views.
Cognitive Complexity: Level 3: Strategic Thinking & Complex Reasoning
MAFS.7.G.1.1
Solve problems involving scale drawings of geometric figures, including computing actual lengths and
areas from a scale drawing and reproducing a scale drawing at a different scale. Cognitive Complexity:
Level 2: Basic Application of Skills & Concepts
MAFS.7.G.1.2
Draw (freehand, with ruler and protractor, and with technology) geometric shapes with given conditions.
Focus on constructing triangles from three measures of angles or sides, noticing when the conditions
determine a unique triangle, more than one triangle, or no triangle. Cognitive Complexity: Level 2: Basic
Application of Skills & Concepts
MAFS.7.G.1.3
Describe the two-dimensional figures that result from slicing three-dimensional figures, as in plane
sections of right rectangular prisms and right rectangular pyramids.
Pre-Requisite Knowledge

Students must understand the composition light, and that it is made up molecules know as
photons.

Students must understand the parts of wave

Students must understand correlation of frequency, wavelength, and intensity

Students must understand that electrons are particles that can be found in matter.
Learning Objectives
 To relate the photoelectric effect to real-world technology

To understand and verify the particle nature of in relation to Nano-Technology
applications

Use scientific processes to verify the effectiveness of the photoelectric effect.
Introduction / Motivation
3
Teacher Demonstration:
Let’s Cool Off with the Photoelectric Effect!
Materials List:
Photoelectric Apparatus with Amplifier (Recommendation: Middle grade teachers may seek
fetter pattern high schools for product inventory before purchase)
LED light
DC Motor/Propeller
Alligator Clips
Voltmeter
Procedure:
1. Assemble the photoelectric effect apparatus with accompanying wires
2. Connect the voltmeter to the apparatus
3. Attach the alligator clips (bottom round tips) to the right side of the apparatus
4. Attach the alligator clip end to the DC Motor/propeller.
Answer the following questions:
1. What the reading on the voltmeter? _____________________________________________
2. Explain the process that resulted in an electric current?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. Does the intensity of light affect the electric current? If so, then why?
______________________________________________________________________________
________________________________________________________________________
4. What is a photon? ___________________________________________________________
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2 The red lines on the metal (left side) plate are electrons. What happens when the photons hit
the electrons? ________________________________________________________________
3. What happens when the electrons reach the light bulb? _____________________________
_________________________________________________________________________
4. When electrons reach the light bulb they complete a circuit, in which the current flow causes
_______________.
Lesson Background & Concepts for Teachers
The photoelectric effect is one of the most famous examples demonstrating the particle nature of
light. The explanation for this effect is what allowed Albert Einstein win the Nobel Prize in
1921. This effect explains that when light is directed on a metal, electrons are released from its
surface. Depending on the amplitude of wavelength of light would make changes in the rate of
flow of electrons from the metal. The theory of the photoelectric effect must explain the
experimental observations of the emission of electrons from an illuminated metal surface to
create an electric current. For a given metal and frequency of radiation, the rate at which
photoelectrons are ejected is directly proportional to the intensity of the incident light. An
increase in the intensity of the incident beam (keeping the frequency fixed) increases the
magnitude of the photoelectric current. Positive electron flow collects on a receiving negatively
charge metal end and creates an electric spark. Continuously photoelectric currents will
ultimately create a continuous flow of an electric current.
Vocabulary / Definitions
Word
Photoelectric Effect
Intensity
Wavelength
Frequency
Electrons
Matter
Electron Current
Light Source
Definition
The photoelectric effect is the observation that many metals emit
electrons when light shines upon them. Electrons emitted in this manner
can be called photoelectrons
The amount of light that is emitted, reflected, transmitted or received, per
unit time
The distance between two crests or two troughs
The amount of wavelengths that pass a point in a given time
Negatively charged particles
Anything that has mass and takes up space
The flow of negatively charged particles.
Any object that produces light.
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Activity:
http://cfcpwork.uchicago.edu/kicp-projects/nsta/2007/pdf/nsta_2007-photoeleclab.pdf
Activity: Using a Soda Can for a Photoelectric Effect
Introduction:
We are going to make an electroscope to learn about the photoelectric effect. We
will first make use of them to detect common static charge. Static charge on an
object comes from removing electron from a metal object. Same goes for the
Photoelectric effect. An electroscope works on the basic principle that two metal
objects with the same charge will repel each other.
Engage:
You should be familiar with static if you’ve ever seen your clothes stuck together
after they’ve been in the dryer or if you’ve ever shocked your friend with a spark
from your finger.
 Why do you think your clothes are sticking together?
 Where do you think the charge on your finger comes from?
Explore
Materials List:
 Styrofoam cup/bowl
 aluminum soda pop can;
recycling bin; free
 sand paper (or something
scratchy like an S.O.S. pad)
 Aluminum foil
 Tape
 Clear plastic ruler
 Brown paper bag (or towel)
Procedure
1. Use sandpaper to remove aluminum from soda can.
2. Attach aluminum strips to soda can lid.
3. Isolate the can and strips from the table. (Placing on Styrofoam may work
best).
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4. Using a clear plastic ruler rub with the towel, one will become negatively
charged and the other positively charged.
5. After removing covering layer from the aluminum can, charge up the
aluminum strips by rubbing the ruler with the towel. Transfer the negative
charge from the ruler to the strips by running the ruler through the strips.
The strips should now be negative and want to repel from each other.
6. With the strips repelling, touch the soda can and discharge it. What
happens to the strips when the charge leaves the electroscope? (Answer:
The strips should relax.)
7. Charge up the strips again with the negatively charged ruler.
8. Move the short-wave UV lamp into position (near, but not touching, the
sanded portion of the soda can), but do not turn it on yet. (This is to show
that the proximity of the UV lamp has little effect on the charged strips.)
9. Now turn on the UV lamp and watch the strips slowly relax, meaning it is
being discharged due to negative charges leaving the aluminum. This is the
photoelectric effect. The energy of the UV light is enough to eject electrons
from the surface of the aluminum.
Answer the following questions:
1) What part of the system is charged? ___________________________________
2) What is the behavior when like charges come in to contact?
________________________
3) What is the behavior when opposite charges come in to contact?
______________________
4) Is this model that you created a good representation of the Photoelectric Effect? Explain.
5) What occurred when the electroscope became charged?
____________________________
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Results Summary:
(Teacher)
When the electroscope becomes charged, positively or negatively, the whole system acquires that
charge. In particular the foil and the metal container becomes charged. Since same charges
repel, the thin foil will be forced away from the sturdier metal because they both have the same
charge. So, when an electroscope is charged, the foil appears to float and turn upwards!
Home-learning
Have the students research real-world applications that utilizes the photoelectric
effect. Make sure that they have descriptions and illustrations for each application.
In addition, have them explain the benefits of the applications.
Lesson Extension Activities
Gizmo (Explore Learning):
Photoelectric Effect Simulation
http://s3.amazonaws.com/el-gizmos/materials/PhotoelectricEffectSE.pdf
Tim and Moby will teach you all about artificial light sources and visible light. You’ll learn
about the two ways in which artificial light can be created, and how fast light can go. Whether
you prefer to light your surroundings with a light bulb or a candle, you’ll discover enough about
each light source to understand how they work! You’ll also gather info on natural sources of
light — like from the sun and even some animals! Plus, Tim and Moby explain how the
electromagnetic spectrum and reflected light help your eyes to see.
Photoelectric Effect Simulation created by PHET
http://phet.colorado.edu/en/simulation/photoelectric
For on-level students, it may be advisable to allow them to explore this simulation prior to the
lab. This simulation can be for students who need supplemental review.
Videos
You tube: How do we turn solar energy to electricity?
https://www.youtube.com/watch?v=EnYjlsGXugo
The photo-electric effect explained
https://www.youtube.com/watch?v=0qKrOF-gJZ4
Discovery Education
Light Energy
http://player.discoveryeducation.com/index.cfm?guidAssetId=4BB5AECD-4E06-456C-8021AD01C8A339A4
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Brain-pop
Light : https://www.brainpop.com/science/energy/light/preview.weml
References
Photoelectric Effect. January 8, 2009. Retrieved from
https://en.wikipedia.org/wiki/File:Photoelectric_effect.png. Accessed 7/10/15.
Beehler, A. 2009. Simple Photoelectric Effect. 2009. Department of Physics and Astronomy;
University of Utah.
http://www.physics.utah.edu/~beehler/newsletterdemos/SimplePhotoelectricEffect.pdf Accessed
7/10/15.
Supporting Program
Research for Experienced Teachers (RET) Program 2015 at Florida International University College of
Engineering and Computing
Acknowledgements
Thank you Research for Experienced Teachers (RET) Program 2015, Program Director: Dr. Masoud
Milani, Mentor: Dr. Hebin Li for all your support.
Classroom Testing Information
This curriculum is assessed for Grade Level 7 in the Miami-Dade County Public Schools District Fall
Science Interim.
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