Hii

I am providing the official NCERT link from where you can download the book in pdf form. All you need to do is enter the class, subject and name of the book and click go.
You will then be redirected to the ebook. There you can find an index and you will be able to download either any chapter or simply you can download complete book.
http://ncert.nic.in/textbook/textbook.htm

Thanks!