This site contains three free books by Emeritus Professor Frank Firk, former Chairman of the Department of Physics, Yale University. The first, Essential Physics 1, is an intensive introduction for potential Physics majors.

The second, Introduction to Groups, Invariants & Particles, is a book for Seniors and Advanced Juniors majoring in the Physical Sciences.

The third, The Age of Einstein, is a brief introduction to Einstein's Theories of Special and General Relativity for the general reader.