Why Do We See Rainbows after it Rains?
Learning Objectives
Assessment Criteria
Benchmarks:
AAAS
Relationship to the driving question
This lesson can be used as a preliminary lesson for discussing electromagnetic waves. The activities allow students to explore how light is refracted through a prism and then relate what they have learned to the lesson’s driving question.
Prior Knowledge/Prior Conceptions
Many middle-school students do not think of light as something that travels from one place to another, and most tend to identify light with its source (e.g., light is in the bulb) or its effects (e.g., a patch of light). Thus, during this lesson, we will explore how light actually travels in a straight line.
Instructional Strategies
During the lesson, we will identify the learning objectives at the beginning of the lesson and review the objectives at the end of the lesson, to ensure the students know what is expected of them in their content knowledge. Also, students will work in groups and pairs as well as a whole class discussions.
Instructional Resources Used
Materials and Set-up Needed
Class set-up
Rows of desks with 2 pushed together or groups of 4 desks would be sufficient for activity.
Time required
2 45-minute class periods or 1 blocked class period
Cautions
The flashlights used in class should not be shined in students’ eyes-make sure to warn students before using the flashlights.
Instructional Sequence
Introducing the lesson:
Show a picture, either in print or on the computer, of the sun. Ask the students:
Now, show a picture of a rainbow. Ask students:
Tell students that at the end of the lesson, they will be able to answer the “rainbow” question. Also, explain learning objectives as highlighted in the beginning, by writing them on the board or handing them out on a piece of paper. This helps to organize the lesson for both the teacher and student.
Body of the lesson:
Show a prism to the students at the front of the classroom.Make sure no light can be shown through the prism, either by dimming classroom lights or pulling down shades at the windows.
Body of the lesson:
Show a prism to the students at the front of the classroom.
- Students will be able to explain how light is refracted into multiple colors of light under proper conditions - and how a rainbow is produced.
- Students will be able to describe the colors that make up white light.
- Students will be able to visualize how light travels and explain that it is not static or simply "appears" in the environment.
- Students will be able to use the colored paper model to visually represent the comparative wavelengths of visible light and explain the scale that is used in the model.
Assessment Criteria
- The students will keep record of their data and observations, as well as a hypothesis and a revision to their hypothesis after the prism activity.
- Class/group discussions and written/drawn explanations of the observations of the prism activity will assess at what level students comprehend the refraction of light to create the visible color spectrum (including identifying the colors of the spectrum.) The way light travels is also included in the class discussions and observation sheet.
- The paper model will allow the teacher to evaluate how well a student can measure and organize a model to represent what they have seen.
Benchmarks:
AAAS
- Light from the sun is made up of a mixture of many different colors of light, even though to the eye the light looks almost white. 4F/M1
- Human eyes respond to only a narrow range of wavelengths of electromagnetic waves - visible light. Differences of wavelength within that range are perceived as differences of color. 4F/M5
Relationship to the driving question
This lesson can be used as a preliminary lesson for discussing electromagnetic waves. The activities allow students to explore how light is refracted through a prism and then relate what they have learned to the lesson’s driving question.
Prior Knowledge/Prior Conceptions
Many middle-school students do not think of light as something that travels from one place to another, and most tend to identify light with its source (e.g., light is in the bulb) or its effects (e.g., a patch of light). Thus, during this lesson, we will explore how light actually travels in a straight line.
Instructional Strategies
During the lesson, we will identify the learning objectives at the beginning of the lesson and review the objectives at the end of the lesson, to ensure the students know what is expected of them in their content knowledge. Also, students will work in groups and pairs as well as a whole class discussions.
Instructional Resources Used
- http://www.discoveryeducation.com/teachers/free-lesson-plans/the-color-spectrum-how-does-it-work.cfm
- http://sciencenetlinks.com/lessons/light-1-making-light-of-science/
Materials and Set-up Needed
- Prism
- Flashlight (optional)
- Colored Markers
- Meter stick or metric ruler (marked in millimeters)
- Scissors
- Scotch tape
- Several pieces of paper in the following colors: red, orange, yellow, green, blue, violet, white, and black (paper will be cut into 1-inch-wide strips)
- Black marker
- Student data sheet
Class set-up
Rows of desks with 2 pushed together or groups of 4 desks would be sufficient for activity.
Time required
2 45-minute class periods or 1 blocked class period
Cautions
The flashlights used in class should not be shined in students’ eyes-make sure to warn students before using the flashlights.
Instructional Sequence
Introducing the lesson:
Show a picture, either in print or on the computer, of the sun. Ask the students:
- How many colors does the sun produce? How many do you see? Where have you seen these color(s)?
- How many colors are found in the light bulb?
Now, show a picture of a rainbow. Ask students:
- Why do we often see rainbows after it rains?
Tell students that at the end of the lesson, they will be able to answer the “rainbow” question. Also, explain learning objectives as highlighted in the beginning, by writing them on the board or handing them out on a piece of paper. This helps to organize the lesson for both the teacher and student.
Body of the lesson:
Show a prism to the students at the front of the classroom.Make sure no light can be shown through the prism, either by dimming classroom lights or pulling down shades at the windows.
- Tell students that at the end of the lesson, they will be able to answer the "rainbow" question. Also, explain learning objectives as highlighted in the beginning, by writing them on the board or handing them out on a piece of paper. This helps to organize the lesson for both the teacher and student.
Body of the lesson:
Show a prism to the students at the front of the classroom.
- Make sure no light can be shown through the prism, either by dimming classroom lights or pulling down shades at the windows.
- Ask students to write the word "refracted on their data sheet as they will have to define it via words and/or picture later in the lesson.
- What will happen if we shine a white light on the prism? What will happen to the light, i.e., will it stay trapped in the prism, will it travel through, etc.? How will the light travel through the prism? (This is important to determine what students believe about light travel!)