This PDF contains the Key concepts used in logarithm, and it also has a variety of questions divided into 3 levels. Exercise 1 being the easy level, Exercise 3 being tough level, and Exercise 2 has toughest questions .Exercise 3 contains questions which are previously asked in IIT Exam. Also i have included answer key with the PDF for your reference. This can be useful for a teacher who wants notes on Logarithm, or can be useful in giving some quality questions to students. Can also be given as a worksheet.