Salient features of the book: (i) Keeping in mind the age group of the students, the matter has been divided into sections and sub-sections so that the students can learn at their own pace. (ii) All new concepts have been developed by class-activity method. The practical hand-on experience of these activities will enable the students to visualise and develop a deeper understanding of the concepts. (iii) Results, wherever possible, have been verified by lab activity method. (iv) Questions in the form of Fill in the Blanks, True / False statements and Multiple Choice Questions, and some Statements I-II type questions given under the heading ‘Objective Type Questions’. (v) Each chapter is followed by a Summary which recapitulates the new terms, concepts and results. (vi) The last section ‘Check Your Progress’, acts as a Unit Test. (vii) Model Question Papers, given at various places, will serve as means for revision and preparation for the exams.