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Subject: Physics
Semester: 1
Period: 1
Week: 5
School Name:
Teacher’s Name:
Subject: Physics
Grade Level: Grade 12
Week & Period: Week 5, Period I
Date:
Topic: Refraction and Dispersion of Light
Sub-topic: Dispersion of Light
Learning Objectives:
By the end of the lesson, learners should be able to:
- Define and explain dispersion of light.
- Distinguish between primary colors and primary pigments.
- Describe the visible spectrum.
- Carry out an experiment to demonstrate dispersion.
- Discuss practical applications of dispersion and color mixing.
Previous Knowledge:
Learners are familiar with refraction, lenses, and the bending of light through different media.
Instructional Materials:
- Prism (glass or plastic)
- White light source (torch or sunlight)
- White screen or cardboard
- Color wheel
- Newton disc
- Colored cellophane or filters
Anticipation (Warm-Up):
Shine white light through a prism. Let learners observe the rainbow spectrum on the screen. Ask:
"Why does white light split into different colors?"
Introduce the concept of dispersion as separation of light into colors due to differences in refraction.
Building Knowledge (Main Lesson):
Definition of Dispersion
Dispersion is the separation of white light into its component colors when it passes through a transparent medium like a prism.
Cause of Dispersion
- Each color in white light travels at a different speed in a medium.
- Violet light bends the most; red bends the least.
- The spread of colors forms a spectrum.
Visible Spectrum
ROYGBIV — Red, Orange, Yellow, Green, Blue, Indigo, Violet
- Red: longest wavelength, lowest frequency
- Violet: shortest wavelength, highest frequency
Primary Colors and Pigments
|
Category |
Primary Colors |
Mixing Produces |
|
Light |
Red, Green, Blue |
White light (additive) |
|
Pigments |
Cyan, Magenta, Yellow |
Black (subtractive) |
Color Mixing
- Red + Green = Yellow
- Red + Blue = Magenta
- Green + Blue = Cyan
- All combined = White (light) or Black (pigment)
Experiment: Demonstrating Dispersion
Title: Splitting White Light with a Prism
Materials: Prism, white cardboard, sunlight or flashlight
Procedure:
- Direct white light into the prism at an angle.
- Place a screen on the other side.
- Observe the spectrum formed.
Observation: Colors appear in order from red to violet on the screen.
Conclusion: Dispersion occurs due to different refractions of different wavelengths.
Learners’ Activities:
- Observe and label the visible spectrum from the prism
- Use colored filters to mix primary colors and record outcomes
- Rotate a Newton disc and observe white color formation
- Complete worksheets on color mixing and dispersion principles
Assessment
Classwork:
- Define dispersion of light.
- What are the primary colors of light?
- Which color bends the most during dispersion?
- Use diagrams to illustrate how a prism splits light.
Homework:
- Draw the spectrum and label all colors in order.
- State two differences between additive and subtractive color mixing.
- Why does violet bend more than red during dispersion?
Expanded Notes:
- Applications of dispersion: rainbow formation, prism spectroscopy, fiber optics
- Newton’s experiments with prisms led to understanding of color in light
- Water droplets in the atmosphere act as prisms to form rainbows
- Dispersion proves that white light is made of many colors
Differentiation (Support & Challenge):
- Use physical prism for visual demonstration
- Let advanced students derive speed of light in different media
- Provide word bank and color-coded notes for struggling learners
- Organize group activities to mix colors and share findings
Teacher’s Reflection:
- Did students understand why colors separate in a prism?
- Were they able to connect color mixing with real-life applications?
- Was the experiment exciting and memorable?
- Should color theory be revised in more detail next class?