Absorption and Transmission of Light

Active learning helps students move beyond memorizing definitions to discovering how light behaves with real objects and tools. When students manipulate colored filters, observe color mixing, and discuss real-world phenomena like the sky’s color, they build durable understanding through direct evidence rather than abstract explanations.

• 8th Grade
• Science
• 4 activities
• 20 min–40 min

Learning Objectives

1. Explain how the absorption and transmission properties of materials determine the wavelengths of light that reach an observer's eye.
2. Analyze how the selective absorption and transmission of light by an object result in its perceived color.
3. Predict the resulting color of an object when illuminated by different colored light sources, based on its absorption and transmission characteristics.
4. Compare and contrast the phenomena of additive color mixing with subtractive color mixing.

Collaborative Problem-Solving

⏱ 40 min·Pairs

Collaborative Problem-Solving: Colored Filters and Objects

Students place colored cellophane filters over a white light source and illuminate objects of different colors. They record what color each object appears under each filter, then write a rule explaining which wavelengths the filter transmits and which wavelengths the object reflects. A red filter over a blue object is the key test case that challenges intuition.

Prepare & details

Explain how materials absorb and transmit specific wavelengths of light.

Facilitation Tip: During the lab, circulate and ask students to verbalize the difference between what they see through the filter and what they see without it, focusing on which wavelengths are passing or being blocked.

Setup: Groups at tables with problem materials

Materials: Problem packet, Role cards (facilitator, recorder, timekeeper, reporter), Problem-solving protocol sheet, Solution evaluation rubric

• Apply
• Analyze
• Evaluate
• Create
• Relationship Skills
• Decision-Making
• Self-Management

Case Study Analysis

⏱ 25 min·Whole Class

Demonstration + Prediction: Additive Color Mixing

Using three flashlights with red, green, and blue filters (or a color-mixing LED board), project circles of colored light that overlap. Students first predict what color the overlapping regions will be, record predictions, then observe the actual result. The class discusses how this differs from mixing paint, building toward the distinction between additive and subtractive mixing.

Prepare & details

Analyze how the interaction of light with matter determines the color we perceive.

Facilitation Tip: For the additive color mixing demonstration, darken the room and use three flashlights with clearly labeled filters to keep the color mixing visible to the whole class.

Setup: Groups at tables with case materials

Materials: Case study packet (3-5 pages), Analysis framework worksheet, Presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Think-Pair-Share

⏱ 20 min·Pairs

Think-Pair-Share: Why Is the Sky Blue?

Students individually write a hypothesis for why the sky is blue and sunsets are red/orange, then compare with a partner. Groups share explanations, and the teacher guides the class toward the concept of differential scattering of wavelengths -- shorter wavelengths scatter more. This connects absorption and transmission principles to a familiar, visible phenomenon.

Prepare & details

Predict the color of an object under different colored lights.

Facilitation Tip: In the Think-Pair-Share on the sky’s color, provide a simple diagram of the electromagnetic spectrum to ground the discussion in concrete wavelengths rather than vague ideas about 'light bouncing around.'

Setup: Standard classroom seating; students turn to a neighbor

Materials: Discussion prompt (projected or printed), Optional: recording sheet for pairs

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Concept Mapping

⏱ 30 min·Small Groups

Concept Mapping: Absorption, Reflection, Transmission

In small groups, students create a concept map connecting the terms: opaque, transparent, translucent, absorbed, reflected, transmitted, wavelength, and color. They must include at least one everyday object example for each connection. Groups share maps on the board and the class identifies common structures and resolves any conflicting connections.

Prepare & details

Explain how materials absorb and transmit specific wavelengths of light.

Facilitation Tip: When building the concept map, give each pair a set of pre-printed terms and arrows so they focus on relationships, not handwriting or layout.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Teaching This Topic

Teach this topic through cycles of prediction, observation, and explanation so students experience cognitive conflict when their expectations don’t match results. Avoid lectures about wavelengths until students have firsthand experience with filters and colored objects. Use everyday examples like colored clothing or traffic lights to anchor abstract ideas in familiar contexts.

What to Expect

Students will confidently explain why an object’s color depends on which wavelengths are absorbed, reflected, or transmitted. They will distinguish additive color mixing from subtractive mixing and use these ideas to predict outcomes in new situations, such as how colored light changes the appearance of objects.

Watch Out for These Misconceptions

Common Misconception

During Lab: Colored Filters and Objects, watch for students who say the red paper itself is 'making' red light.

What to Teach Instead

Prompt students to hold the red paper under white light with and without the green filter. Ask them to trace the path of light and explain why the paper’s color changes or disappears, reinforcing that the paper only reflects certain wavelengths it receives.

Common Misconception

During Demonstration + Prediction: Additive Color Mixing, watch for students who claim mixing red and green paint produces the same result as mixing red and green light.

What to Teach Instead

After the demonstration, have students compare the additive mix on a white screen to a subtractive mix on paper. Ask them to describe how each process changes the wavelengths that reach their eyes.

Common Misconception

During Concept Mapping: Absorption, Reflection, Transmission, watch for students who label white as 'absorbs everything' and black as 'reflects nothing.'

What to Teach Instead

Challenge students to test white and black objects under colored light. Ask them to revise their maps to show how white reflects most wavelengths and black absorbs most wavelengths, with clear exceptions noted.

Assessment Ideas

Exit Ticket

After Lab: Colored Filters and Objects, provide students with a blue piece of paper and a red filter. Ask them to write: 1. What color light does the blue paper absorb most? 2. What color light does the blue paper reflect or transmit most? 3. What color will the blue paper appear when viewed through the red filter? Explain why.

Quick Check

During Demonstration + Prediction: Additive Color Mixing, present students with red and green flashlights. Ask them to predict the combined color, explain their reasoning using absorption, transmission, and reflection, then test their prediction.

Discussion Prompt

After Think-Pair-Share: Why Is the Sky Blue?, pose the question: 'Why does a white shirt appear white under sunlight but might look slightly yellow under a warm incandescent bulb?' Guide students to discuss how the spectrum of light emitted by different sources affects the wavelengths absorbed, transmitted, or reflected by the shirt's material.

Extensions & Scaffolding

• Challenge students to design a colored filter that makes a red apple appear black under white light, then test it using the lab materials.
• For students who struggle with additive vs. subtractive mixing, provide a side-by-side comparison tray: one side with colored filters over a white surface, the other with colored filters over black paper.
• Have advanced students research how digital screens produce color using tiny red, green, and blue subpixels, then create a short presentation explaining the connection to additive color mixing.

Key Vocabulary

Wavelength	The distance between successive crests of a wave, especially points in the electromagnetic wave, such as light. Different wavelengths correspond to different colors.
Absorption	The process by which a material takes in light energy, converting it into other forms of energy, such as heat.
Transmission	The process by which light passes through a material without being absorbed or reflected.
Reflection	The bouncing of light off the surface of an object. The color we see is often the light that is reflected.
Visible Spectrum	The portion of the electromagnetic spectrum that is visible to the human eye, consisting of the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet.