Unit 15 Light, Colours and Beyond

Topic

The disappearing coin

Curriculum Link

15.6 Refraction and Its Practical Uses

Estimated Lesson Time

80 minutes

Introduction

Firstly, students are engaged to attend to an interesting effect of total internal refraction by watching video clip. Then students learn to use simple ray diagrams to explain the 'disappearance of coin' (Task 1) and use 'parallax' to locate the position of visual image (Task2). Based on the understanding of total internal refraction and skills to locate the image, students could conduct an experiment to explore the relationship between apparent length and real length in refraction (Task 3). Finally, teacher could provide students an opportunity to elaborate their understanding of apparent length in two daily life examples.

Key Question

Is something visible to us really exists?

Learning Objectives

In this activity, the students should be able to

  1. Explain the formation of mirage and refraction scenarios with simple ray diagrams;
  2. Use simple ray diagrams to identify the path of light (SP6);
  3. Use the method 'no parallax' to locate the position of virtual image (SP4);
  4. Observe and record data during experiment (SP1);
  5. Draw conclusion by interpreting the data collected (SP5).

Teaching Plan

Task (Time) Brief Description Materials Objectives

Engagement
(15 min)

Students are engaged to learn refraction by watching video clips of mirage in Death valley

Teachers probe students' ideas in explaining 'mirage' using ray diagrams.

(1)

Exploration & Explanation
(20 min)

In task 1, students explore the effect of refraction with the 'disappearance' and re-appearance' of a coin into a cup. Teachers explain the phenomena using simple ray diagram.

(2)

Explanation & Exploration
(15 min)

Teacher explains how an image could be located by the method of 'no parallax'.

[Optional: Teacher may distinguish the differences between real image and virtual image.]  

 (3)

Elaboration
(25 min)

Teacher explains the meaning of real depth and apparent depth of an object. Then, ask students to find the relationship between the real depth and apparent depth of a bolt in a large container filling with water.

[Optional: Teachers may ask students to explain the findings with ray diagram.]

(4) & (5)

Elaboration
(5 min)

Ask students to explain some every day examples by the concept of refraction with simple ray diagram. (Task 4)

(1)

*Apparatus and materials required: