Context
Light is a fundamental essence in everyday life, allowing us to see the world around us. But how can the behavior of light create shadows and penumbras? This is the central question we will explore in this project, shedding light (pun intended) on the fundamentals behind the formation of shadows and penumbras.
Light travels in straight lines from its source until it hits or is reflected by an object. When an opaque object blocks the light, a shadow is created. However, not all shadows are created equal. When the light source is a point, the shadow is completely dark and is called an umbra. But when the light source is extended, like the sun, the shadow has both an umbra (darker region) and a penumbra (less dark region). This is because sunlight hits the object from different angles, allowing some of the light to bend around the object.
Shadows and penumbras have important applications in the fields of art, physics, and astronomy. Artists use shadows and penumbras to create a sense of three-dimensionality and depth in their paintings and drawings. In physics, these concepts are important for understanding the propagation of light and the formation of images. In astronomy, understanding shadows and penumbras is crucial for predicting and understanding events such as solar and lunar eclipses. Additionally, observations of the shadows and penumbras of planets and their moons provide valuable information about the atmospheres of these celestial bodies.
To further your understanding of shadows and penumbras, I recommend the following resources:
- Interactive Physics, from the Institute of Physics of the University of São Paulo - This link addresses not only Penumbra and Shadow, but also how they are formed and their applications in real life.
- Color and Light Theory, from the Physics Project of the University of São Paulo - This link offers a broader view on light and its properties.
- Book "Optics and Thermodynamics", by Alonso and Finn - An excellent resource for those who wish to delve deeper into topics of optics and thermodynamics.
Activity: "Light and Shadows – Exploring Penumbra and Umbra"
PROJECT GOAL:
The goal of this project is to investigate the phenomenon of shadow and penumbra formation, using concepts and tools from geometrical optics and trigonometry. Students will be able to differentiate between penumbra and umbra, understand what causes each, and how to identify examples of both in the real world.
PROJECT DESCRIPTION:
Students, divided into groups of 3 to 5, will design and build an experiment that demonstrates the formation of shadows and penumbras. The experiment must be conducted in a dark, closed environment so that students have better control over the light sources. They must consider different properties of light, such as its direction, intensity, and color, to create shadows and penumbras.
The project will be divided into two parts: in the first, students must research the topic, plan, and build the experiment. In the second, they must conduct the experiment, record the results, and write a report on the project.
REQUIRED MATERIALS:
- Black cardboard
- Light bulbs of different sizes and colors
- Opaque objects of different shapes and sizes
- Ruler
- Protractor
- Graph paper
- Camera to document the results
PROJECT STEP-BY-STEP:
Step 1: Research and planning
Students must research the formation of shadows and penumbras, and how light behaves when it hits an opaque object. Based on this knowledge, they must plan an experiment that can demonstrate this phenomenon.
Step 2: Building the experiment
Using the materials listed above, students will build the experiment. This involves selecting and positioning the objects and light source(s) to produce shadows and penumbras.
Step 3: Conducting the experiment
Students will conduct the experiment and document the results. It is important that they record the different scenarios, such as changing the position of the light and the objects, to conclude each scenario.
Step 4: Writing the report
Based on the observations made during the experiment, students will write a report, divided into four sections: Introduction, Development, Conclusions and Bibliography.
In the Introduction, students must contextualize the topic, explain its importance and application in the real world and describe the objective of the project.
In the Development, students must explain the theory behind the formation of shadows and penumbras, describe the experiment in detail, including the methodology used, and finally, present and discuss the results obtained.
In the Conclusion, students must resume the main points of the work and discuss the lessons learned and the conclusions drawn about the project.
In the Bibliography, students must list the sources of information used throughout the project.
PROJECT DELIVERABLES:
The deliverables include the hands-on experiment, photographic documentation of the scenarios tested and the written report.
The report should be organized following the guidelines above and must include a detailed discussion of the results, demonstrating the group's understanding of the concepts involved.
The hands-on experiment and photographic documentation serve as a visual complement to the report and help illustrate the concepts discussed. The quality of the experimentation and documentation will be taken into consideration in the final evaluation of the project.
The deliverables must demonstrate not only the students' knowledge of the subject, but also their teamwork, problem-solving and critical and creative thinking skills.
