Our aim in this set of lectures is to give an introduction to critical
phenomena that emphasizes the emergence of and the role played by diverging
length-scales. It is now accepted that renormalization group gives the basic
understanding of these phenomena and so, instead of following the traditional
historical trail, we try to develop the subject in a way that emphasizes the
length-scale based approach.Comment: Revtex, 26 pages, 2 figures. Lectures given at the SERC School on
"Field theoretic methods in Condensed matter physics", held at MRI,
Allahabad, Indi
