Refraction of light through a prism

Content Standards

In this lesson, learners will demonstrate an understanding of how light is refracted through a prism and dispersed into its constituent colors. They will recognize and represent the phenomena using diagrams, real-life examples (rainbow, fountain), and simple measurements (angle of deviation).

Performance Standards

Students will be able to:

Identify and represent refraction of light through a triangular glass prism.
Understand the key terms: angle of prism, angle of deviation, dispersion, and spectrum.
Compare refraction in a glass slab versus a prism.
Explain how sunlight splits into seven colours and how they recombine.
Apply the concept to real-world phenomena such as rainbows and fountains.

Alignment Standards

Reference: NCERT Book Alignment

The lesson is aligned with the NCERT Grade 10 Science Textbook, Chapter 10: “The Human Eye and the Colourful World”, Section 10.3: Refraction of light through a prism.

Learning Objectives

By the end of the lesson, students will be able to:

Define and explain refraction of light through a prism.
Draw and label a ray diagram showing the incident ray, the refracted ray, the emergent ray, and the angle of deviation.
Describe and explain the dispersion of white light into VIBGYOR.
Demonstrate how two prisms can recombine the spectrum into white light.
Relate the concepts to natural phenomena like rainbow formation.

Prerequisites (Prior Knowledge)

Basic understanding of refraction of light (from earlier topic: refraction through a rectangular glass slab).
Familiarity with the terms incident ray, refracted ray, emergent ray, and normal.
General awareness of natural phenomena like rainbows.

Introduction

In this session, students will explore how a prism bends light and creates a spectrum of colours. Through activities, demonstrations, and virtual lab simulations, they will connect the scientific concept with real-life observations, such as rainbows after rain or light seen through waterfalls.

Timeline (40 Minutes)

Title	Approximate Duration	Procedure	Reference Material
Engage	5	Begin the session by asking: “Why does a rainbow apprear after rain?”	Slides
Explore	10	Ask: “Think of places you have seen colourful light effects.”	Slides
Explain	10	The teacher explains the prism structure, the prism angle, and the deviation angle. Then, introducing dispersion with a diagram and the VIBGYOR sequence, the Teacher Shows Newton’s two-prism experiment using a 3D model using VR Lab.	Slides and Virtual Lab
Evaluate	10	Students will attempt the Self Evaluation task on LMS.	Virtual Lab
Extend	5	Ask: “Can two prisms be arranged in such a way that they cancel each other’s dispersion but still produce deviation? Explain with an example.” Explanation: Two prisms can cancel dispersion but still cause deviation. If two identical prisms are placed in opposite directions, the dispersion produced by the first prism is cancelled by the second prism, so white light emerges without forming a spectrum. However, the entire beam still gets deviated because both prisms together bend the light in the same overall direction.	Slides

Refraction of light through a prism

Introduction

In this lesson, students will learn about how light bends (refraction) when it passes through a triangular glass prism and how it splits into seven colors (dispersion). Through demonstrations, ray diagrams, and real-life examples like rainbows, students will explore how prisms change the direction of light and why this concept is important in understanding natural phenomena.

Theory

1. Why Study Refraction and Dispersion?

Have you ever wondered why a rainbow appears after rain or light looks colorful when passing through a glass crystal? These fascinating effects are due to refraction and dispersion. We must first learn how light behaves inside a prism to understand rainbows and spectrum formation. For example, Imagine learning about hundreds of plants without organizing them — it would be overwhelming! But if we group them into herbs, shrubs, and trees, it becomes much easier to learn and compare.

2. What is Refraction and Dispersion?

Refraction: The bending of light when it passes from one medium to another.
Dispersion: Splitting white light into its component colors (VIBGYOR) when it passes through a prism.

3. Key Components:

Triangular Prism: A transparent solid with two triangular bases and three rectangular sides.
Incident Ray (PE): The incoming ray of light striking the prism.
Refracted Ray (EF): The ray bending towards the normal as it enters the prism.
Emergent Ray (FS): The ray bending away from the normal as it exits the prism.
Angle of Deviation (∠D): The angle between the incident and emergent rays.
Spectrum (VIBGYOR): The band of seven colors produced when white light is dispersed.

4. Process

Step 1: Light enters the prism at surface AB (air → glass) and bends towards the normal.
Step 2: Light passes through the prism and emerges at surface AC (glass → air), bending away from the normal.
Step 3: The emergent ray is not parallel to the incident ray but deviates by angle D.
Step 4: White light splits into seven colors because each color bends by a different amount (red least, violet most).

Example: When sunlight passes through a prism, it splits into VIBGYOR. If a second prism is inverted, these colors recombine into white light (Newton’s experiment).

5. Visual Representation

Ray Diagram: Incident ray (PE), refracted ray (EF), emergent ray (FS), and angle of deviation.
Spectrum Diagram: White light splitting into seven colours arranged from violet (top) to red (bottom).
Real Example: Rainbow after rain, caused by water droplets acting like tiny prisms.

6. Applications / Why is it Useful?

Explains rainbow formation in nature.
Used in spectroscopy to study light and materials.
Helps in designing optical instruments like spectrometers.
Demonstrates light behaviour in physics experiments.
Basis for technologies like fiber optics and dispersion prisms in cameras.

Vocabulary

This is the list of vocabulary terms used throughout the lesson.

Prism: A transparent solid with flat, angled surfaces that refract light.
Refraction: The bending of light as it passes from one medium to another.
Angle of Prism: The angle between two refracting surfaces of a prism.
Angle of Deviation (∠D): The angle between the incident and emergent rays.
Dispersion: Splitting of white light into its component colours by a prism.
Spectrum: The band of colours (VIBGYOR) formed due to dispersion.
VIBGYOR: Acronym for Violet, Indigo, Blue, Green, Yellow, Orange, Red.
Rainbow: A natural spectrum formed due to dispersion and internal reflection of sunlight by raindrops.

Refraction of light through a prism

Introduction

Virtual Lab Activity: The Human Eye and the Colorful World | Refraction of light through a prism

Category: Informative

Key Features

Features:

Clear and intuitive user interface with step-by-step navigation.
Real-time updates with visuals of prism and rays as learners progress.
Visual representation of key concepts using images and animations for each step.
Optional quiz or challenge mode to test understanding of refraction and dispersion.

Step-by-Step Procedure for VR Experience

Step-by-step Procedure for VR Experience

Open the Virtual Lab – Access the simulation link.

Step 1 — What is a Prism

Learn that a prism is a transparent block with flat angled faces.
Observe how a ray bends due to refraction.
(Use with Image 1: Prism introduction)

Step 2 — Shape of a Glass Prism

Explore the structure with two triangular bases and three rectangular faces.

(Use with Image 2: Triangular prism shape)

Step 3 — Dispersion: Making a Spectrum

Pass white light through the prism.
Watch it split into seven colors (VIBGYOR).
(Use with Image 3: Spectrum dispersion)

Step 4 — Recombination with Two Prisms

Place a second prism inverted to the first.
See how the colors recombine into white light, proving sunlight has seven colors.
(Use with Image 4: Recombination experiment)