Physics - 0625 CIE

Light

Overview

Every time you glance in a mirror you are using a law of physics that is exact to a fraction of a degree: light bounces off a smooth surface so that the angle it arrives at equals the angle it leaves. That single rule lets us predict exactly where an image appears and why your reflection looks the size and distance it does.

In this topic you will define the normal and the angles of incidence and reflection, state and use the law of reflection, and describe the image formed by a plane mirror. You will also learn to construct and measure ray diagrams for reflection, the skill that turns the law into accurate predictions.

Objectives

Define and use the terms normal, angle of incidence and angle of reflection
Describe the formation of an optical image by a plane mirror and give its characteristics, i.e. same size, same distance from mirror, virtual
State that for reflection, the angle of incidence is equal to the angle of reflection; recall and use this relationship
[Supplement] Use simple constructions, measurements and calculations for reflection by plane mirrors

Lesson Note

Mirrors steer light in periscopes, dental mirrors, car wing mirrors and laser instruments. The law of reflection is one of the most reliable rules in physics, and exam questions test whether you can name the angles correctly, apply the law, and describe the image a plane mirror forms.

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Lesson Evaluation

Congratulations on completing the lesson on Light. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

The angle of incidence is measured between the incident ray and the: A. mirror surface B. reflected ray C. normal D. horizontal Answer: C
A ray hits a plane mirror with an angle of incidence of 30 degrees. The angle of reflection is: A. 60 degrees B. 30 degrees C. 15 degrees D. 90 degrees Answer: B
The image formed by a plane mirror is: A. real and larger B. virtual and the same size C. real and inverted D. virtual and smaller Answer: B
A ray strikes a mirror at 20 degrees to the surface. The angle of reflection from the normal is: A. 20 degrees B. 40 degrees C. 70 degrees D. 90 degrees Answer: C
An object is 5 cm in front of a plane mirror. Its image is: A. 5 cm in front B. 10 cm behind C. 5 cm behind D. on the mirror Answer: C