• Introduction

    Changes in schools
    This text book is part of the reform of the school curriculum in Rwanda: that is 
    changes in what is taught in schools and how it is taught. It is hoped this will 
    make what you learn in school useful to you when you leave school, whatever 

    you do then.

    In the past, the main thing in schooling has been to learn knowledge – that is 
    facts and ideas about each subject. Now the main idea is that you should be 
    able to use the knowledge you learn by developing skills or competencies
    These skills or competencies include the ability to think for yourself, to be 
    able to communicate with others and explain what you have learnt, and to be 
    creative, that is developing your own ideas, not just following those of the 
    teacher and the text book. You should also be able to find out information and 
    ideas for yourself, rather than just relying on what the teacher or text book 

    tells you.

    Activity-based learning 
    This means that this book has a variety of activities for you to do, as well 
    as information for you to read. These activities present you with material or 
    things to do which will help you to learn things and find out things for yourself. 
    You already have a lot of knowledge and ideas based on the experiences you 
    have had and your life within your own community. Some of the activities, 

    therefore, ask you to think about the knowledge and ideas you already have.

    In using this book, therefore, it is essential that you do all the activities. 
    You will not learn properly unless you do these activities. They are the most 

    important part of the book.

    In some ways this makes learning more of a challenge. It is more difficult to 
    think for yourself than to copy what the teacher tells you. But if you take up 
    this challenge you will become a better person and become more successful 

    in your life.

    Group work
    You can also learn a lot from other people in your class. If you have a problem 
    it can often be solved by discussing it with others. Many of the activities in the 
    book, therefore, involve discussion or other activities in groups or pairs. Your 
    teacher will help to organise these groups and may arrange the classroom so 
    you are always sitting in groups facing each other. You cannot discuss properly 

    unless you are facing each other.

    Research
    One of the objectives of the new curriculum is to help you find things out 
    for yourself. Some activities, therefore, ask you to do research using books 
    in the library, the internet if your school has this, or other sources such as 
    newspapers and magazines. This means you will develop the skills of learning 
    for yourself when you leave school. Your teacher will help you if your school 

    does not have a good library or internet.

    Icons
    To guide you, each activity in the book is marked by a symbol or icon to show 

    you what kind of activity it is. The icons are as follows:

    C

    V

    PHY

    Unit 1 :Thin lenses