Physics - Senior Secondary 2 - Light waves

TERM: 1^ST TERM

WEEK: 10

Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes for each of 5 periods
Date:
Subject: Physics
Topic: Light Waves
Subtopics:
• Refraction of light through triangular glass block
• Angle of minimum deviation
• Totally reflecting prisms

SPECIFIC OBJECTIVES:
By the end of the lesson, students should be able to:

1. Explain the phenomenon of refraction of light through a triangular glass block.
2. Determine the angle of minimum deviation in a triangular prism.
3. Understand the concept of totally reflecting prisms and their applications.
4. Use Snell's law to calculate the angle of refraction.

INSTRUCTIONAL TECHNIQUES:
• Explanation
• Demonstration
• Questions and answers
• Hands-on activity: Verifying Snell’s law using a triangular glass block
• Group work: Investigation of the angle of minimum deviation

INSTRUCTIONAL MATERIALS:
• Triangular glass blocks
• Protractors
• Light sources
• Whiteboard markers
• Physics textbook
• Videos on refraction and Snell’s law

INSTRUCTIONAL PROCEDURES
PERIOD 1-5

PRESENTATION

STEP 1: INTRODUCTION
• The teacher will introduce the concept of refraction and its importance in the study of light.
• Students will be asked to recall what they know about Snell’s law and the bending of light when it passes through different mediums.

STEP 2: EXPLANATION
• The teacher explains the concept of refraction and how light bends when it passes from one medium to another.
• Introduction of the triangular glass block and the phenomenon of light passing through the prism.
• Explanation of the angle of minimum deviation, the angle at which light refracts in the least amount through the prism.
• The teacher demonstrates the refraction of light through a triangular glass block.

STEP 3: DEMONSTRATION
• The teacher demonstrates how light refracts through the triangular glass block, observing the change in direction.
• Students are encouraged to use protractors to measure the angle of deviation and calculate the angle of refraction using Snell’s law.
• Discussion of totally reflecting prisms and their uses in optical instruments.

STEP 4: ACTIVITY
• The students will work in pairs to verify Snell’s law using a triangular glass block.
• Students will use a light source, protractors, and triangular glass blocks to measure angles and calculate refraction.
• Group work: Students will attempt to determine the angle of minimum deviation for the triangular prism.

STEP 5: NOTE TAKING
• The teacher will summarize the lesson on the board:

• Refraction occurs when light passes through different media, causing a change in speed and direction.
• The angle of minimum deviation is the smallest angle at which light refracts through the prism.
• Snell’s law is used to calculate the relationship between angles of incidence and refraction.

NOTE:

• Snell's Law:
  n₁ * sin(θ₁) = n₂ * sin(θ₂)
  where n₁ and n₂ are the refractive indices of the two media, and θ₁ and θ₂ are the angles of incidence and refraction respectively.
• Angle of Minimum Deviation:
  The angle at which the light refracts the least when passing through a triangular prism.

EVALUATION

1. What is Snell’s law, and how is it applied in refraction?
2. What is the angle of minimum deviation, and why is it important?
3. Describe the process of light refraction through a triangular glass block.
4. How is Snell's law used to calculate refraction angles?

CLASSWORK:
• Verify Snell’s law using a triangular glass block and record the angles of incidence and refraction.
• List the steps to determine the angle of minimum deviation.

CONCLUSION:
• Review the students’ work and provide feedback on their calculations.
• Encourage the students to reflect on the significance of refraction in optical instruments.