Timeless and collectible, The Feynman Lectures on Physics are essential reading, not just for students of Physics, but for anyone seeking an insightful introduction to the field from the inimitable Richard P. Feynman. "When I look at The Feynman Lectures on Physics, I feel a very personal sense of closeness to them," said Feynman, looking back at the origins of these books. Ranging from probability amplitudes to spin, two-state systems, propagation in a crystal lattice, semiconductors, symmetry, and conservation laws, the lectures collected in Volume III of The Feynman Lectures on Physics stand as a monument to clear exposition and deep insightand to Feynman's deep connection with the field.