Beacon Lesson Plan Library

Photoelectric Devices

Cynthia Youngblood
Santa Rosa District Schools

Description

Students view a teacher-made PowerPoint presentation on how photoelectric devices work, and then they answer FCAT-like questions on the material presented.

Objectives

The student selects and uses strategies to understand words and text, and to make and confirm inferences from what is read, including interpreting diagrams, graphs, and statistical illustrations.

The student determines the main idea and identifies relevant details, methods of development, and their effectiveness in a variety of types of written material.

The student drafts and revises writing that: is focused, purposeful, and reflects insight into the writing situation; has an organizational pattern that provides for a logical progression of ideas; has effective use of transitional devices that contribute to a sense of completeness; has support that is substantial, specific, relevant, and concrete; demonstrates a commitment to and involvement with the subject; uses creative writing strategies as appropriate to the purpose of the paper; demonstrates a mature command of language with precision of expression; has varied sentence structure; and has few, if any, convention errors in mechanics, usage, punctuation, and spelling.

The student understands how knowledge of energy is fundamental to all the scientific disciplines (e.g., the energy required for biological processes in living organisms and the energy required for the building, erosion, and rebuilding of the Ear

Materials

-EZ Pro Projector or LCD Screen or Computer lab with Presentation loaded at each computer station
-Computer
-PowerPoint presentation (See Attached File)
-Hard copies of the presentation for each student
-Projection screen
-Copies of questions for each student (See Assessment)
-Pen or pencil

Preparations

1. Download PowerPoint presentation Photoelectric Devices.
2. Make hard copies of PowerPoint Presentation Photoelectric Devices for each student.
3. Create a Question sheet for students to assess the information in the presentation. Copy and paste the questions listed in the assessment section into a Word Document. This can then be duplicated for students.

Procedures

Note: Students should be acquainted with the following scientific terms before they do this lesson: atoms, photons, electrons, radiation, light wave, and semiconductors. The teacher needs to review these.


1. As an introduction, before you show the PowerPoint Presentation, ask students to complete a [KWL] Chart about photoelectric devices. Have them to divide a sheet a paper into three columns. Mark [K] at the top of the first column. Mark [W] at the top of the second column. Mark [L] at the top of the third column.

2. Tell students to list things that they know about photoelectric devices in the first column marked [K]. Give students about five minutes to make their lists. Have students share the things on their lists. (Examples: garage door openers, elevators, and remote controls.)

3. In the second column, tell students to write what they would like to learn about photoelectric devices in the column marked [W]. (Examples: How do they work? What are some other devices that work using photoelectricity?) Ask them to share responses.

4. Tell students that at the end of the presentation, they will complete the third column marked [L] with things that they learned about photoelectric devices. (Examples: Photoelectric cells, photo cells, electric eyes, photoemission, photoconductivity, and photovoltaic.) Ask them to share responses.

5. Teacher formatively evaluates students’ [KWL] Charts.

6. Teacher shows and narrates the PowerPoint presentation on Photoelectric Devices.

7. Tell students at the end of the presentation to complete the third column marked [L] with things that they learned about photoelectric devices. (Examples: Photoelectric cells, photo cells, electric eyes, photoemission, photoconductivity, and photovoltaic.) Ask them to share responses.

8. At the end of the presentation, distribute hard copies of the presentation to help students answer the questions.

9. Students answer questions. (See Assessment.)

10. Teacher evaluates students’ answers to questions. (See Assessment for rubric scale for extended response.)

Assessments

Students’ KWL Charts will be formatively assessed.

After viewing the presentation, students will answer FCAT-like questions. Students should answer 85% of these questions accurately in order to show mastery. The written extended response will be evaluated using the following FCAT Reading Scoring Rubric:

2 points- The response indicates that the student has a complete understanding of the reading concept embodied in the task. The student has provided a response that is accurate, complete, and fulfills all the requirements of the task. All necessary support and/or examples are included, and the information given is clearly text-based. Any extensions beyond the text are relevant to the task.

1 point- The response indicates that the student has a partial understanding of the reading concept embodied in the task. The student has provided a response that may include information that is essentially correct and text-based, but the information is too general or too simplistic. Some of the support and/or examples may be incomplete or omitted.

0 points- The response is inaccurate, confused, and/or irrelevant, or the student failed to respond to the task.


Directions: After viewing the PowerPoint presentation on Photoelectric Devices, answer the following questions.

Questions on Photoelectric Devices

The student understands how knowledge of energy is fundamental to all the scientific disciplines.

The student determines the main idea and identifies relevant details, methods of development, and their effectiveness in a variety of types of written material.

1. What is a photoelectric effect?
2. What happens when light strikes certain light-sensitive materials?
3. List three things that make use of the photoelectric effect?
4. List three kinds of photoelectric cells.
5. What scientist first explained photoemissive cells?
6. Explain photoemission.
7. List some things that use photoemissive cells.
8. What are photoconductive cells?
9. What is a good example of an application of photoconductivity?
10. Explain the process that activates a streetlight.
11. How does a burglar alarm work?
12. What are some other examples of electric eyes?
13. Are photovoltaic cells similar to photoconductivity?
14. Explain how photovoltaic cells work.
15. What is the energy efficiency of most present-day photovoltaic cells?
16. Photovoltaic cells that operate on solar light have so far been used for very low-power applications. List several items that use photovoltaic cells.
17. Larger photovoltaic cell units have been used to power ______________
_________________________and___________________________and _____________. (Fill in the blanks.)

The student drafts and revises writing that is focused, purposeful, and reflects insight into the writing situation.

18-20. Extended response question: Choose one of the kinds of photoelectric cells and explain how we use it in our daily lives.


ANSWERS:

1. A photoelectric effect is any effect in which light energy is converted to electricity.
2. It may cause them to give electrons.
It may change their ability to conduct electricity.
It may cause them to develop an electrical potential or voltage across two surfaces. (These are called photoelectric devices.)
3. A photo electric cell, a photo cell, or an electric eye.
4. Photoemissive cells, photoconductive cells, or photovoltaic cells.
5. Albert Einstein
6. Light, like all other radiation, is made up of small particles called photons. The amount of energy the photons have depends on the frequency of light. The frequency of light is the number if times that a light wave vibrates in a second. The higher the frequency, the more energy the photons have. If a photon hits an atom of a certain material, it may be absorbed by an electron of that material. However, if the photon has enough energy, the electron is ejected, or emitted, from the atom. In this way, light energy changes into electrical energy. If wires are attached to a photoemittive material, the electrons can flow along the wires, forming an electric current.
7. Motion picture projectors to read film sound tracks, a photographer’s slave flash unit.
8. Results from light hitting a semiconductor. Semiconductors contain free, negatively charged electrons. A free electron is an electron that has left its atom and so is not bound to it. When the electron leaves its atom, it creates a positive charge in the atom. The positive charge attracts an electron from another atom. This process repeats itself, creating an electric current. When light falls on certain semiconductors, the number of electrons leaving their atoms increases. This increases the current.
9. A streetlight
10. As daylight fades, the electrical current in the streetlight’s semiconductor comes to a stop. This activates a switch that turns the streetlight on.
11. They have electric eyes that operate on the principle of photoconductivity. When a person walking through the beam of light interrupts the light source, a switch is activated that triggers the alarm.
12. Automatic door openers, elevator doors, and supermarket scanners.
13. Yes
14. In this effect, light falls on two semiconductors or on a metal and a semiconductor sandwiched together. A boundary develops between these two substances. Free electrons build up along the boundary but cannot flow across it. However, if the two substances are connected in a circuit, then the electrons can flow across it.
15. Seven to eleven percent
16. Calculators, watches, and cameras
17. Space satellites, experimental airplanes and automobiles
18-20.Answers will vary.

Extensions

Students should be acquainted with the following scientific terms before they view this presentation; therefore, the teacher needs to review these:
atoms, photons, electrons, radiation, light wave, and semiconductors.

Students could create their own PowerPoint presentations about another scientific topic.

Attached Files

A Power Point presentation.     File Extension: ppt

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