Contextualization

Theoretical Introduction

A wave reflection is what happens when a wave hits a surface that does not absorb it and forces it to bounce back to the media it came from. This is a fundamental concept in Physics that applies to several types of waves, including light, sound, and water surface waves.

During reflection, the wave can behave in two ways: it can either keep its direction or invert it. It all depends on the properties of the media and the interface where the wave reflects. There are two general reflection types we study: specular (or regular) reflection, which happens when a wave falls on a smooth surface, like a mirror, and diffuse reflection, which occurs when the wave falls on an irregular surface.

It is important to note that, during reflection, the wave's frequency and wave length remain the same, even if its direction changes. This means that the wave continues to be the same, it is just going in a different direction.

Examples in Practice

Wave reflection is a phenomenon that we can observe all the time around us. Sound, for example, is a wave that bounces all over the objects around us, which is why a room's acoustics can change so much based on the materials and positions of the objects on that room. Light reflection is another common example, since it is how we are able to see the world around us. Without it, we wouldn't be able to see anything!

Professionally, wave reflection has many important applications, like in civil engineering and architecture, where it is used to plan the acoustics of spaces such as theaters and concert halls. In medicine, the reflection of ultrasound waves is what allows us to create images of the inside of the body through ultrasounds.

Practical Activity

Activity title

"Unveiling the Wave Reflection Phenomenon: An Experiment Using Strings and Sound"

Project Goal

This project's main goal is to observe and reflect on the wave reflection phenomenon, understanding how it happens in real life. Through practical experimentation and group discussions, the students will explore the theoretical concept, put it into practice, and evaluate their findings.

Detailed Project Description

The students will perform a series of practical experiments where they will generate waves with a string and also with a sound wave generating app in their cell phones. The students will register their observations, discuss the results with the group, and analyze what those results tell us about the theory of wave reflection.

Required Materials

• A string of at least 2 meters in length
• A smartphone with a sound wave generation app (There are many available for free on Android and iOS)
• A piece of cardboard
• Tape
• A silent environment
• A notebook for taking notes

Step-by-Step Guide

1. Split the class into groups of 3 to 5 students.
2. Each group should stretch the string and fix it at one end, while the other end will be left loose.
3. One of the members of the group should move the free end of the string quickly, generating a wave. The group should then observe what happens when the wave reaches the fixed end (that is, the wave reflection).
4. The students should register their observations, considering the wave's characteristics before and after reflection.
5. Now, the groups should use the sound wave generating app to generate a sound wave in the direction of the cardboard and observe what happens.
6. Again, the group should take notes of their observations and discuss and compare the results from both steps of the experiment.
7. The students should discuss the wave reflection phenomenon based on their observations and on the theoretical knowledge they got from studying the suggested readings and from the classes they attended.

Project Deliverables

Each group, after the experiment, must deliver:

1. Written Report: The document should have four main parts, as described below:
   • Introduction: The group should include context about the theme, its relevance, and its real-life applications. The goal of the project should be clear.
   • Development: Here, the students should explain the theory of wave reflection, describe in detail the activity that was done, which methodology was used, and the results that were achieved. The students should discuss the results with the theory studied.
   • Conclusion: In this section the students should go back over the main points of the project, state what they learned, and which conclusions can be drawn from it.
   • Bibliography: The sources the group used to complete the project, such as books, websites, videos, etc.

It is worth remembering that this is a group project and all members should collaborate. Everyone should take part in the elaboration of each part of the report, sharing their observations, conclusions, and learning.

2. Oral Presentation: Each group will present their findings to the class in a presentation that should last 10 minutes at most, in which they can show the experiment they did and share their conclusions. It is important that all members of the group actively participate in the presentation.

The project will last a week, starting on the day the theme is introduced to the class.