8.286 The Early Universe (Fall 2013, MIT OCW). Instructor: Professor Alan Guth. The Early Universe provides an introduction to modern cosmology. The first part of the course deals with the classical cosmology, and later part with modern particle physics and its recent impact on cosmology.
(from ocw.mit.edu)

Lecture 18 - Cosmic Microwave Background Spectrum and the Cosmological Constant, Part I

In this lecture, the professor continued to talk about the black-body radiation, then talked about cosmic microwave background spectrum and the cosmological constant.