CK PART II TEXTBOOK FOR CLASS XI CK CK www.com ISBN 81-7450-508-3 (Part-I) ISBN 81-7450-566-0 (Part-II) First Edition April 2006 Chaitra 1928 ALL RIGHTS RESERVED Reprinted q No part of this publication may be reproduced, stored in a retrieval October 2006 Kartika 1928 system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior February 2008 Magha 1929 permission of the publisher. January 2009 Magha 1930 q This book is sold subject to the condition that it shall not, by way of January 2010 Magha 1931 trade, be lent, re-sold, hired out or otherwise disposed of without the publisher’s consent, in any form of binding or cover other than that in January 2012 Magha 1932 which it is published. January 2013 Magha 1933 q The correct price of this publication is the price printed on this page, January 2014 Magha 1935 Any revised price indicated by a rubber stamp or by a sticker or by any other means is incorrect and should be unacceptable. PD 400T RNB © National Council of Educational OFFICES OF THE PUBLICATION Research and Training, 2006 DIVISION, NCERT NCERT Campus Sri Aurobindo Marg New Delhi 110 016 Phone : 011-26562708 108, 100 Feet Road Hosdakere Halli Extension Banashankari III Stage Bangalore 560 085 Phone : 080-26725740 Navjivan Trust Building P.Navjivan Ahmedabad 380 014 Phone : 079-27541446 CWC Campus Opp.
Dhankal Bus Stop Panihati Kolkata 700 114 Phone : 033-25530454 CWC Complex ` 85.00 Maligaon Guwahati 781 021 Phone : 0361-2674869 Publication Team Head, Publication : Ashok Srivastava Division Chief Production : Kalyan Banerjee Officer Chief Business : Gautam Ganguly Manager Chief Editor : Naresh Yadav Printed on 80 GSM paper with NCERT (Contractual Service) watermark Editor : R. Bhardwaj Published at the Publication Division by (Contractual Service) the Secretary, National Council of Production Assistant : Prakash Veer Singh Educational Research and Training, Sri Aurobindo Marg, New Delhi 110 016 and printed at M/s. Saraswati Printing Press Cover and Illustrations A-95, Sector – 5, Noida – 201 301 (UP) Shweta Rao CK CK www.com FOREWORD The National Curriculum Framework (NCF), 2005 recommends that children’s life at school must be linked to their life outside the school. This principle marks a departure from the legacy of bookish learning which continues to shape our system and causes a gap between the school, home and community.
The syllabi and textbooks developed on the basis of NCF signify an attempt to implement this basic idea. They also attempt to discourage rote learning and the maintenance of sharp boundaries between different subject areas. We hope these measures will take us significantly further in the direction of a child-centred system of education outlined in the National Policy on Education (1986). The success of this effort depends on the steps that school principals and teachers will take to encourage children to reflect on their own learning and to pursue imaginative activities and questions.
We must recognise that, given space, time and freedom, children generate new knowledge by engaging with the information passed on to them by adults. Treating the prescribed textbook as the sole basis of examination is one of the key reasons why other resources and sites of learning are ignored. Inculcating creativity and initiative is possible if we perceive and treat children as participants in learning, not as receivers of a fixed body of knowledge. These aims imply considerable change is school routines and mode of functioning.
Flexibility in the daily time-table is as necessary as rigour in implementing the annual calendar so that the required number of teaching days are actually devoted to teaching. The methods used for teaching and evaluation will also determine how effective this textbook proves for making children’s life at school a happy experience, rather than a source of stress or boredom. Syllabus designers have tried to address the problem of curricular burden by restructuring and reorienting knowledge at different stages with greater consideration for child psychology and the time available for teaching. The textbook attempts to enhance this endeavour by giving higher priority and space to opportunities for contemplation and wondering, discussion in small groups, and activities requiring hands-on experience.
The National Council of Educational Research and Training (NCERT) appreciates the hard work done by the textbook development committee responsible for this book. We wish to thank the Chairperson of the advisory group in science and mathematics, Professor J. Narlikar and the Chief Advisor for this book, Professor A. Joshi for guiding the work of this committee.
Several teachers contributed to the development of this textbook; we are grateful to their principals for making this possible. We are indebted to the institutions and organisations which have generously permitted us to draw upon their resources, material and personnel. We are especially grateful to the members of the National Monitoring Committee, appointed by the Department of Secondary and Higher Education, Ministry of Human Resource Development under the Chairpersonship of Professor Mrinal Miri and Professor G. Deshpande, for their valuable time and contribution.
As an organisation committed to systemic reform and continuous improvement in the quality of its products, NCERT welcomes comments and suggestions which will enable us to undertake further revision and refinement. Director New Delhi National Council of Educational 20 December 2005 Research and Training CK CK www.com TEXTBOOK DEVELOPMENT COMMITTEE CHAIRPERSON, ADVISORY GROUP FOR TEXTBOOKS IN SCIENCE AND MATHEMATICS J. Narlikar, Emeritus Professor, Chairman, Advisory Committee, Inter University Centre for Astronomy and Astrophysics (IUCCA), Ganeshbhind, Pune University, Pune CHIEF ADVISOR A. Joshi, Professor, Honorary Visiting Scientist, NCRA, Pune (Formerly at Department of Physics, University of Pune) MEMBERS Anuradha Mathur, PGT , Modern School, Vasant Vihar, New Delhi Chitra Goel, PGT, Rajkiya Pratibha Vikas Vidyalaya, Tyagraj Nagar, Lodhi Road, New Delhi Gagan Gupta, Reader, DESM, NCERT, New Delhi H.
Pradhan, Professor, Homi Bhabha Centre of Science Education, Tata Institute of Fundamental Research, V. Purav Marg, Mankhurd, Mumbai N. Panchapakesan, Professor (Retd.), Department of Physics and Astrophysics, University of Delhi, Delhi P. Srivastava, Professor (Retd.), Director, CSEC, University of Delhi, Delhi P.
Mohanty, PGT, Sainik School, Bhubaneswar P. Agarwal, Reader, Regional Institute of Education, NCERT, Sachivalaya Marg, Bhubaneswar R.), DESM, NCERT, New Delhi S. Rai Choudhary, Professor, Department of Physics and Astrophysics, University of Delhi, Delhi S. Dash, Reader, DESM, NCERT, New Delhi Sher Singh, PGT, Lodhi Road, New Delhi S.
Prabhakara, PGT, DM School, Regional Institute of Education, NCERT, Mysore Thiyam Jekendra Singh, Professor, Department of Physics, University of Manipur, Imphal V. Srivastava, Reader, DESM, NCERT, New Delhi MEMBER-COORDINATOR B. Sharma, Professor, DESM, NCERT, New Delhi CK CK www.com ACKNOWLEDGEMENTS The National Council of Educational Research and Training acknowledges the valuable contribution of the individuals and organisations involved in the development of Physics textbook for Class XI. The Council also acknowledges the valuable contribution of the following academics for reviewing and refining the manuscripts of this book: Deepak Kumar, Professor, School of Physical Sciences, Jawaharlal Nehru University, New Delhi; Pankaj Sharan, Professor, Jamia Millia Islamia, New Delhi; Ajoy Ghatak, Emeritus Professor, Indian Institute of Technology, New Delhi; V.
Sundara Raja, Professor, Sri Venkateswara University, Tirupati, Andhra Pradesh; C. Adgaonkar, Reader (Retd), Institute of Science, Nagpur, Maharashtra; D. Desai, Lecturer (Retd), Ruparel College, Mumbai, Maharashtra; F. Surve, Lecturer, Nowrosjee Wadia College, Pune, Maharashtra; Atul Mody, Lecturer (SG), VES College of Arts, Science and Commerce, Chembur, Mumbai, Maharashtra; A.
Das, PGT, St. Xavier’s Senior Secondary School, Delhi; Suresh Kumar, PGT, Delhi Public School, Dwarka, New Delhi; Yashu Kumar, PGT, Kulachi Hansraj Model School, Ashok Vihar, Delhi; K. Upadhyay, PGT, Jawahar Navodaya Vidyalaya, Muzaffar Nagar (U. Gogia, PGT, Kendriya Vidyalaya, Gole Market, New Delhi; Vijay Sharma, PGT, Vasant Valley School, Vasant Kunj, New Delhi; R.
Dass, Vice Principal (Retd), Balwant Ray Mehta Vidya Bhawan, Lajpat Nagar, New Delhi and Parthasarthi Panigrahi, PGT, D. CLW Girls School, Chittranjan, West Bengal. The Council also gratefully acknowledges the valuable contribution of the following academics for the editing and finalisation of this book: A. Mahajan, Professor (Retd), Indian Institute of Technology, Mumbai, Maharashtra; D.
Desai, Lecturer (Retd), Ruparel College, Mumbai, Maharashtra; V. Raybagkar, Reader, Nowrosjee Wadia College, Pune, Maharashtra and Atul Mody, Lecturer (SG), VES College of Arts, Science and Commerce, Chembur, Mumbai, Maharashtra. Special thanks are due to M. Chandra, Professor and Head, DESM, NCERT for her support.
The Council also acknowledges the efforts of Deepak Kapoor, Incharge, Computer Station, Inder Kumar, DTP Operator; Saswati Banerjee, Copy Editor; Abhimanu Mohanty and Anuradha, Proof Readers in shaping this book. The contributions of the Publication Department in bringing out this book are also duly acknowledged. CK CK www.com PREFACE More than a decade ago, based on National Policy of Education (NPE-1986), National Council of Educational Research and Training published physics textbooks for Classes XI and XII, prepared under the chairmanship of Professor T., with the help of a team of learned co-authors. The books were well received by the teachers and students alike.
The books, in fact, proved to be milestones and trend-setters. However, the development of textbooks, particularly science books, is a dynamic process in view of the changing perceptions, needs, feedback and the experiences of the students, educators and the society. Another version of the physics books, which was the result of the revised syllabus based on National Curriculum Framework for School Education-2000 (NCFSE-2000), was brought out under the guidance of Professor Suresh Chandra, which continued up to now. Recently the NCERT brought out the National Curriculum Framework-2005 (NCF-2005), and the syllabus was accordingly revised during a curriculum renewal process at school level.
The higher secondary stage syllabus (NCERT, 2005) has been developed accordingly. The Class XI textbook contains fifteen chapters in two parts. Part I contains first eight chapters while Part II contains next seven chapters. This book is the result of the renewed efforts of the present Textbook Development Team with the hope that the students will appreciate the beauty and logic of physics.
The students may or may not continue to study physics beyond the higher secondary stage, but we feel that they will find the thought process of physics useful in any other branch they may like to pursue, be it finance, administration, social sciences, environment, engineering, technology, biology or medicine. For those who pursue physics beyond this stage, the matter developed in these books will certainly provide a sound base. Physics is basic to the understanding of almost all the branches of science and technology. It is interesting to note that the ideas and concepts of physics are increasingly being used in other branches such as economics and commerce, and behavioural sciences too.
We are conscious of the fact that some of the underlying simple basic physics principles are often conceptually quite intricate. In this book, we have tried to bring in a conceptual coherence. The pedagogy and the use of easily understandable language are at the core of our effort without sacrificing the rigour of the subject. The nature of the subject of physics is such that a certain minimum use of mathematics is a must.
We have tried to develop the mathematical formulations in a logical fashion, as far as possible. Students and teachers of physics must realise that physics is a branch which needs to be understood, not necessarily memorised. As one goes from secondary to higher secondary stage and beyond, physics involves mainly four components, (a) large amount of mathematical base, (b) technical words and terms, whose normal English meanings could be quite different, (c) new intricate concepts, and (d) experimental foundation. Physics needs mathematics because we wish to develop objective description of the world around us and express our observations in terms of measurable quantities.
Physics discovers new properties of particles and wants to create a name for each one. The words are picked up normally from common English or Latin or Greek, but gives entirely different meanings to these words. It would be illuminating to look up words like energy, force, power, charge, spin, and several others, in any standard English dictionary, and compare their CK CK www.com vii meanings with their physics meanings.