Lesson Plan | Traditional Methodology | Flat Mirror: Image Formation

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to provide a clear understanding of the learning objectives for the students. This helps to direct the students' focus towards the key concepts that will be addressed, ensuring that they understand the importance of studying plane mirrors and how it applies to real-world physics problems. Additionally, it will facilitate the organization of the lesson and allow students to know what is expected of them by the end of the session.

Main Objectives

1. Recognize what a plane mirror is.

2. Verify that the distance from the plane mirror to the image is equal to the distance from the mirror to the object.

3. Solve problems involving plane mirrors.

Introduction

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to establish an initial connection between the theoretical content and the practical application of plane mirrors in the students' daily lives. This initial context helps to capture students' interest and show the relevance of the topic. Additionally, by introducing curiosities about the history and applications of mirrors, the lesson becomes more engaging and interesting, facilitating the understanding of the concepts that will be addressed later.

Context

To start the lesson on plane mirrors, it is important to contextualize students about the presence and importance of mirrors in our daily lives. Plane mirrors are widely used in various environments, from our homes in bathrooms and living rooms to commercial applications, such as in stores and beauty salons. They are essential for performing simple daily tasks, such as grooming, shaving, or applying makeup, and also have scientific and technological applications, such as in optical instruments and security systems.

Curiosities

An interesting curiosity is that plane mirrors have been used since antiquity. The first mirrors were made of polished stone, such as obsidian, and only later were made of polished metal. However, the manufacturing technology for mirrors has improved significantly over the centuries, resulting in the glass mirrors with silver or aluminum coatings that we use today. Furthermore, the Law of Reflection, which governs the behavior of plane mirrors, is fundamental for the design of telescopes and other advanced optical devices.

Development

Duration: (45 - 50 minutes)

The purpose of this stage of the lesson plan is to deepen the students' theoretical knowledge about plane mirrors, ensuring they understand the laws of reflection and the image formation process. Through detailed explanations and visual examples, students will be able to visualize and solve practical problems involving plane mirrors. This stage also aims to provide opportunities for the practical application of the learned concepts, reinforcing understanding through exercises and diagrams.

Covered Topics

1. Definition of Plane Mirror: Explain what a plane mirror is. A plane mirror is a flat reflective surface that forms virtual images of objects. The images formed are upright and the same size as the object. 2. Laws of Reflection: Detail the laws of reflection. The first law of reflection states that the angle of incidence is equal to the angle of reflection. The second law of reflection indicates that the incident ray, the reflected ray, and the normal to the mirror's surface at the point of incidence all lie in the same plane. 3. Image Formation: Explain the process of image formation in a plane mirror. The image formed by a plane mirror is virtual, upright, and the same size as the object. The image appears to be behind the mirror at a distance equal to the distance of the object in front of the mirror. 4. Distance from Image to Mirror: Check the relationship between the distance from the object to the mirror and the distance from the image to the mirror. Use diagrams to illustrate that the distance from the image to the mirror is equal to the distance from the object to the mirror. 5. Properties of the Image: Discuss the properties of the image in a plane mirror. The image is virtual (cannot be projected onto a screen), upright (not inverted), the same size as the object, and symmetrical with respect to the mirror.

Classroom Questions

1. 1. An object is located 3 meters from a plane mirror. What will be the distance between the object and its image? 2. 2. Draw a ray diagram to show the formation of the image of an object positioned in front of a plane mirror. 3. 3. If a plane mirror is rotated at an angle of 15 degrees, what will be the new angle of reflection for a light ray that strikes perpendicularly to the mirror before being rotated?

Questions Discussion

Duration: (20 - 25 minutes)

The purpose of this stage of the lesson plan is to review and consolidate students' understanding of the concepts presented, ensuring that they can apply the laws of reflection and the properties of plane mirrors in solving problems. Through detailed discussion of the questions and active engagement of the students, this stage aims to clarify doubts, reinforce learning, and stimulate critical reflection on the practical use of plane mirrors.

Discussion

• 1. An object is located 3 meters from a plane mirror. What will be the distance between the object and its image?

• Explain that, according to the properties of plane mirrors, the distance from the image to the mirror is equal to the distance from the object to the mirror. Therefore, if the object is 3 meters from the mirror, the image will also be 3 meters from the mirror, totaling a distance of 6 meters between the object and its image.

• 2. Draw a ray diagram to show the formation of the image of an object positioned in front of a plane mirror.

• Draw a detailed ray diagram on the board, showing an object in front of a plane mirror. Draw rays of light emanating from the object, hitting the mirror and reflecting according to the Law of Reflection (angle of incidence equals angle of reflection). Show the formation of the virtual image behind the mirror at the same distance as the object is in front of the mirror.

• 3. If a plane mirror is rotated at an angle of 15 degrees, what will be the new angle of reflection for a light ray that strikes perpendicularly to the mirror before being rotated?

• Explain that initially, a light ray that strikes perpendicularly to the mirror has an angle of incidence of 0 degrees. When the mirror is rotated by 15 degrees, the new angle of incidence will be 15 degrees, and, according to the first Law of Reflection, the angle of reflection will also be 15 degrees.

Student Engagement

1. ❓ Question for Reflection: Why is the image formed by a plane mirror always virtual and cannot be projected onto a screen? 2. ❓ Discussion: How can the symmetry of images in plane mirrors be applied practically, such as in security systems or art? 3. ❓ Reflection: If you were to draw a simple periscope using plane mirrors, how would the Law of Reflection help in the design of the device? 4. ❓ Debate: What are some everyday situations where understanding the properties of plane mirrors might be useful?

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage of the lesson plan is to review and consolidate the main points covered during the lesson, ensuring that students have a clear and cohesive understanding of the concepts presented. By recapping the content and highlighting the connection between theory and practice, this stage reinforces the importance of the subject and helps solidify learning.

Summary

• What a plane mirror is.
• Laws of Reflection.
• The process of image formation in a plane mirror.
• The relationship between the distance from the object to the mirror and the distance from the image to the mirror.
• Properties of the image formed by a plane mirror.

The lesson connected theory with practice by demonstrating how plane mirrors are used in everyday situations, such as in bathrooms and beauty salons, and in technological applications, such as in optical instruments and security systems. Diagrams and practical examples helped visualize and apply the laws of reflection in image formation, facilitating the understanding of theoretical concepts.

The study of plane mirrors is important in daily life, as these devices are widely used in various everyday situations. Understanding how images are formed and the properties of these images can help students apply this knowledge in different contexts, such as in the design of objects that use mirrors and in understanding optical phenomena.