Lesson Plan | Traditional Methodology | Geometric Optics: Apparent Position

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage is to provide a clear and detailed overview of the main concepts that will be addressed during the lesson. This will help students understand what is expected of them by the end of the lesson and the importance of the topic within the context of Physics. The definition of clear objectives will also guide the teacher in structuring and conducting the lesson, ensuring that all essential points are covered.

Main Objectives

1. Explain the concept of the apparent position of a submerged object in different media.

2. Demonstrate how to calculate the real and apparent position of an object using principles of geometric optics.

3. Present practical examples and solve problems involving the refraction of light in different media.

Introduction

Duration: (10 - 15 minutes)

🎯 Purpose: The purpose of this stage is to provide an engaging and contextualized introduction to the theme of the Apparent Position. By connecting the content with practical situations and curiosities, students will be more receptive and interested, better understanding the relevance of the topic in daily life and in Physics. Furthermore, this introduction will prepare the ground for the more detailed explanations that will be provided throughout the lesson.

Context

📚 Context: To start the lesson on Geometric Optics and the Apparent Position, present students with the idea of how light behaves when passing from one medium to another. Use everyday examples, such as observing a spoon in a glass of water, where the spoon appears to be broken or displaced. Highlight that this phenomenon is caused by the refraction of light, which alters the path of light rays when they change from one medium to another with different refractive indices.

Curiosities

🔍 Curiosity: Did you know that this same principle is used in glasses and cameras? The refraction of light is essential for correcting vision and capturing sharp images. Additionally, observing the apparent position of a submerged object can be crucial in activities such as fishing, where the real position of fish in the water is different from the position we see.

Development

Duration: (40 - 50 minutes)

🎯 Purpose: The purpose of this stage is to deepen students' understanding of the apparent position and the refraction of light. By addressing key topics and providing practical examples, students will be able to apply the theory to real situations, strengthening their ability to solve problems involving refraction and the apparent position of objects. Solving questions in class will allow students to practice the concepts learned and clarify their doubts immediately, ensuring a solid understanding of the content.

Covered Topics

1. 📘 Law of Refraction (Snell-Descartes Law): Explain that when light passes from one medium to another, its speed changes, resulting in a change in the direction of light rays. The relationship between the angles of incidence and refraction is given by Snell-Descartes' Law: n1sin(θ1) = n2sin(θ2), where n is the refractive index of the medium. 2. 📘 Refractive Index: Detail that the refractive index of a medium is a measure of how light propagates in that medium. It is defined as the ratio between the speed of light in a vacuum and the speed of light in the medium. Typical refractive indices include air (approximately 1), water (approximately 1.33), and glass (approximately 1.5). 3. 📘 Apparent Position: Explain that the apparent position of a submerged object is where the observer perceives that the object is located due to the refraction of light. Use diagrams to illustrate how light refracts when passing from water to air, making the object appear closer to the surface than it actually is. 4. 📘 Calculation of Real and Apparent Position: Teach how to use Snell-Descartes' Law to calculate the real position of a submerged object knowing its apparent position, and vice versa. Provide the formula and practical examples to clarify the calculations. 5. 📘 Practical Examples: Present practical examples such as observing a coin at the bottom of a glass of water and fishing, where fish appear to be in a position different from their actual position. Solve problems detailing each step of the calculation.

Classroom Questions

1. 1️⃣ A coin is at the bottom of a glass of water (refractive index = 1.33). If the real depth of the coin is 6 cm, what is the apparent depth when viewed vertically? 2. 2️⃣ A stick is partially submerged in water, making an angle with the surface. Draw a diagram showing the path of the light rays and explain why the stick appears to be broken. 3. 3️⃣ A fish is 2 meters deep in a lake. Calculate the apparent depth of the fish when viewed directly from above (consider the refractive index of water as 1.33).

Questions Discussion

Duration: (20 - 25 minutes)

🎯 Purpose: The purpose of this stage is to ensure that students consolidate their understanding of the concepts covered in the lesson through detailed discussion of the resolved questions. By reviewing the answers and explanations, the teacher can clarify doubts and reinforce key points. Furthermore, student engagement with reflective questions allows for deeper contextualized learning, encouraging them to think critically about the content.

Discussion

• 1️⃣ Question 1: A coin is at the bottom of a glass of water (refractive index = 1.33). If the real depth of the coin is 6 cm, what is the apparent depth when viewed vertically?

Explanation: The apparent depth can be calculated using the refraction formula. The relationship between real depth (d_real) and apparent depth (d_apparent) is given by:

d_apparent = d_real / n

Substituting the values, we have: d_apparent = 6 cm / 1.33 ≈ 4.51 cm. So, the apparent depth is approximately 4.51 cm.

• 2️⃣ Question 2: A stick is partially submerged in water, making an angle with the surface. Draw a diagram showing the path of the light rays and explain why the stick appears to be broken.

Explanation: When drawing the diagram, it should show the refraction of light rays at the water-air interface. The light rays passing from the stick into the water change direction as they cross the surface due to the difference in the refractive index. This causes the submerged part of the stick to appear to be in a different position than the part above water, creating the illusion that the stick is broken. The change in angle is explained by Snell-Descartes' Law.

• 3️⃣ Question 3: A fish is 2 meters deep in a lake. Calculate the apparent depth of the fish when viewed directly from above (consider the refractive index of water as 1.33).

Explanation: Again, we use the refraction formula to find the apparent depth. Here, d_real = 2 m and n = 1.33. Applying the formula:

d_apparent = d_real / n

Substituting the values, we have: d_apparent = 2 m / 1.33 ≈ 1.50 m. Therefore, the apparent depth of the fish is approximately 1.50 m.

Student Engagement

1. ❓ Why is the apparent depth always less than the real depth when we observe a submerged object? 2. ❓ How can the refraction of light affect the accuracy of activities such as fishing or underwater photography? 3. ❓ If the refractive index of water were higher, how would that affect the apparent position of submerged objects? 4. ❓ Can we apply the concept of apparent position in other contexts besides water? What would those contexts be?

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage is to consolidate the learning from the lesson by recapping the main points and reinforcing the understanding of the concepts addressed. Additionally, by connecting theory with practice and highlighting the relevance of the topic, this stage helps solidify knowledge and demonstrate the applicability of concepts in the daily life of students.

Summary

• Light refracts when passing from one medium to another with different refractive indices, altering its path.
• Snell-Descartes' Law relates the angles of incidence and refraction through the refractive indices of the media.
• The apparent position of a submerged object is where the observer perceives the object to be, due to the refraction of light.
• Calculations of real and apparent position can be made using Snell-Descartes' Law and the refractive indices of the media.
• Practical examples, such as observing a submerged coin or fishing, illustrate how objects appear to be in different positions from their real ones due to refraction.

The lesson connected the theory of light refraction and Snell-Descartes' Law with practical examples from everyday life, such as observing submerged objects and fishing. By solving real problems, students were able to see how theoretical concepts are applied in practical situations, reinforcing their understanding of the apparent position of submerged objects.

The topic presented is important for daily life, as light refraction affects various activities, such as observing objects in water, fishing, and the design of glasses and cameras. Understanding refraction and apparent position helps explain common visual phenomena and improve accuracy in activities that depend on underwater vision.