D i s c o v e r i n g L i g h Discovering t : F MARÍA VIÑAS PEÑA u n Editor E Light x p e r Light is an element that draws together many areas of human knowledge: i m Fun Experiments physics, chemistry, biology, astronomy, engineering, and art. Moreover, e optical phenomena and the technologies based on them are widespread in n t with Optics our daily lives. However, it can be difficult to understand or explain these s phenomena. What is light? Where are optics and photonics present in our w i lives and in nature? What lies behind different optical phenomena? What is t h an optical instrument? How does the eye resemble an optical instrument? O MARÍA VIÑAS PEÑA How can we explain human vision? p ti Editor c The book you are holding, written by a group of young scientists, answers s these questions and many more to help you to get to know the exciting world of optics and photonics. It is intended for the general public, with an emphasis on students at all levels of secondary education. A variety of VIÑAS easy-to-follow experiments related to different optical phenomena and technologies are presented. All of them are preceded by an explanation of the concepts and accompanied by numerous illustrations and curiosities. All of it is meant for you to have fun with optics and photonics! P.O. Box 10 Bellingham, WA 98227-0010 ISBN: 9781510639355 SPIE Vol. No.: PM324 Fun Experiments with Optics Front Matter.indd 1 4/23/2021 1:45:03 PM Front Matter.indd 2 4/23/2021 1:45:03 PM Fun Experiments with Optics Sara Aissati Rocío Gutiérrez Contreras Xoana Barcala Gosende Juan Luis Méndez González Clara Benedí García Roberta Morea Camilo Florian Baron Javier Nuño del Campo Francesca Gallazzi Pablo Pérez Merino Mario García Lechuga Daniel Puerto García Juan Luis García Pomar María Viñas Peña Coordinator: María Viñas Peña Front Matter.indd 3 4/23/2021 1:45:04 PM Library of Congress Control Number: 2020944342 ISBN: 978-1-5106-3936-2 e-ISBN: 978-1-5106-3935-5 DOI: 10.1117/3.2579764 English translation of Descubriendo la luz: Experimentos divertidos de óptica Copyright © 2018 CSIC Translated by Alexandra Stephens and Craig Cavanagh ISBN: 978-84-00-10789-5 e-ISBN: 978-84-00-10790-1 NIPO: 833-21-043-3 e-NIPO: 833-21-044-9 DL: M-11258-2021 In cooperation with the OSA Foundation Published by SPIE P.O. Box 10 Bellingham, Washington 98227-0010 USA Phone: +1 360.676.3290 Fax: +1 360.647.1445 Email: [email protected] Web: http://spie.org Copyright © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE) Cover image courtesy of Francesca Gallazzi All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means without written permission of the publisher. The content of this book reflects the work and thought of the authors. Every effort has been made to publish reliable and accurate information herein, but the publisher is not responsible for the validity of the information or for any outcomes resulting from reliance thereon. SAFETY NOTE: All of the experiments in this book are intended to be performed under adult supervision. Appropriate and reasonable caution is required at all times, and the recommendations in the activities in this book cannot replace sound judgment. The authors and publisher disclaim all liability for any damage, mishap, or injury that may occur from engaging in the activities featured in this book. Printed in the United States of America Last edited 10 May 2021 For updates to this book, visit http://spie.org and type “PM324” in the search field Front Matter.indd 4 4/23/2021 1:45:04 PM Contents Preface by María J. Yzuel vii Introduction ix Acknowledgments xi Safety rules for the use of laser pointers xiii 1. What is light? 1 2. Lights sources and detectors 37 3. Optical instruments 61 4. The human eye: a biological camera 105 5. Light in nature 139 6. Light–based technologies 175 Review of what we have learned 209 Glossary 225 Index 233 About the Authors 235 v Front Matter.indd 5 4/23/2021 1:45:05 PM Front Matter.indd 6 4/23/2021 1:45:05 PM Preface It is my great pleasure to write these lines as the preface for the book Discovering Light: Fun Experiments with Optics, by Maria Viñas, project coordinator, with the collabora- tion of 14 co-authors. The book was written first in Spanish with the title Descubriendo la luz: Experimentos divertidos de óptica and published in 2018 by the CSIC (Consejo Superior de Investigaciones Cientificas, Spanish National Research Council) and the publisher Catarata Books. This book has had a great success in Spain, and I hope that this edition in English will also be very successful worldwide. The group of co-authors had more than ten years of experience working together before the publication of this book. The authors met as young researchers at the Institute of Optics (IO-CSIC), and they were members at some point of the IO-CSIC OSA student chapter. They organized very valuable activities and experiments for students and also for the public in general. The book that you have in your hands will help you to love optics, to understand what light is, and to play with light. It is organised by topics of great interest, going from the fun- damental concept of light, as wave and as particle (photon), to light-based technologies. Some chapters in this book are indeed new and necessary for broadening the field that the teachers show to students, such as the human eye: a biological photographic camera, light in nature, and many easy and original experiments included in the book. All chapters have the same structure: first, an introduction to the fundamentals of optics that teachers and students should review for the specific topic under study; secondly, a description of the experiments with questions about what the students have learned. At the end of the book, the authors give the answers to these questions in an extended and open way that will help teachers and students to deepen their knowledge of a particular field. There is a need for books and courses that might help teachers to introduce experi- ments in optics in their laboratories with students. The experiments in this book are very inspiring and amusing; they open the way to discuss with the students the things that they see in real life, and the students can be drawn to study more deeply the fundamentals. For young people, experiments playing with light are magical. It is important in the education process to open the world to students for exploration and to help children to find their passion for discovering things. The collaboration of the two major optics societies—SPIE (The international Society for Optics and Photonics) and OSA (The Optical Society)—with the CSIC in this English version of this book makes this project very attractive because it will reach a very wide audience. This book can inspire the members of the student chapters of both societies to organise outreach activities with students and adults for learning optics in an amusing way. vii Front Matter.indd 7 4/23/2021 1:45:05 PM OSA and SPIE collaborated very actively with the major optics and physics societies to approach UNESCO and ask the United Nations General Assembly to declare 2015 as “The International Year of Light and Light-based Technologies.” The success of this celebration lead to a new goal: to get an International Day of Light (IDL). It was approved by UNESCO, and 2018 was the first year we could celebrate the IDL on May 16th. The IO-CSIC and the authors of this book have participated very actively with the organisation of education and outreach events in schools and in the Institute of Optics. The International Year of Light and Light-based Technologies, as well as the IDL, are global initiatives to raise awareness of how optical technologies promote sustainable development and provide solutions to worldwide challenges in energy, education, agri- culture, communications and health. Light is central to life, science, technology, art and culture. Light can promote education at all levels. Light technology drives development. There was a United Nations observance that aimed to raise awareness of the achievements of light science and its applications, and its importance to humankind. Books like this communicate to society as a whole the importance of light in today’s world and inspire a new generation of students and interest them in studying science. People are familiar with many natural light phenomena that we see daily and with light-based technologies because we use many devices in which light plays a crucial role. However, they do not always know the science behind them. If it is explained in an easy and amusing way, we can attract many people who will be surprised by the beauty of science. I hope that the readers of this book enjoy it as much as I have. I wish that the readers will be inspired by the experiments described in this book for their outreach activities. María J. Yzuel1 1 SPIE 2009 President Fellow Member of OSA, SPIE, IOP, and EOS Honorary Member of SEDOPTICA and RSEF Professor Emeritus, Universitat Autònoma de Barcelona, Spain Chair of the Spanish Committee for the International Day of Light viii Preface Front Matter.indd 8 4/23/2021 1:45:05 PM Introduction Light is an element that draws together many areas of human knowledge (physics, chemistry, biology, astronomy, engineering, art, etc.); moreover, optical phenomena and the technologies based on them are widespread in our daily lives. However, it can be difficult to understand or explain these phenomena. What is light? Where are optics and photonics present in our lives? What lies behind different optical phenomena? What is an optical instrument? How does the eye resem- ble an optical instrument? How can we explain human vision? What are everyday optical technologies based on? Where is optics found in nature? The book you are holding, written by a group of young scientists, attempts to answer these questions and many more, and help you to get to know the exciting world of optics and photonics. Our aim is to look at optics from all sides, covering both basic phenomena occurring in nature and the very latest applications and technologies. Although we want to reach out to anyone interested in science, we have taken care to include experiments and explana- tions covering the light-related topics on the syllabus for high school level. Our experience in performing demonstrations at primary and secondary schools, as well as the general public, has taught us that the best way to reach our goals is through experimentation and interpretation of results. We have developed a set of exercise cards to help you complete the different experiments step by step (color-coded by level of complexity), after which the challenge is to show what you have learned. We provide help to fully understand the experiments, with an introduction to all the necessary concepts at the beginning of each chapter, as well as plenty of interesting facts. Chapter 1 looks at the physical properties of light, how it is described, how it travels and how it behaves on interaction with different materials. Some of the key words in this chapter are wave, photon, reflection, refraction, diffraction and interference. In Chapter 2, we explore the different sources and detectors of light that are so com- monplace in our daily lives. It includes experiments using extraordinary light emitters like lasers and building “invisible” light detectors. Chapter 3 shows how you can use simple optical elements such as lenses, mirrors and prisms to build different optical instruments. We will focus on understanding how light travels and images are formed using these items and how we can manipulate light using optical instruments such as cameras, microscopes and telescopes. ix Front Matter.indd 9 4/23/2021 1:45:06 PM