Open course ware

PROFESSOR: Last time, we spoke about photons in the context of an interferometer. The Mach-Zehnder interferometer. And we saw the very unusual properties of photons and interference, and how relatively simple interference a effect can be used to produce a very surprising measurement. Today we're going to backtrack and go from the beginning, and think about photons as physicists did 100 years ago, and how, by thinking about photons, they pretty much came up with quantum mechanics. So we want to trace this back. And the best place to start, probably, is with a photoelectric effect. The photoelectric effect is an experiment done by Hertz in 1887, in which he irradiated plates. That means shine light, high energy beams of light, on metal plate, and he found that electrons were released. Those were called photo electrons. And therefore, you would get a photoelectric current from those electrons. So this is the effect we want to discuss now, is the photoelectric effect. And...

Any time you begin a communication, whether face-to-face, in writing, or over the phone, it's important to think about why you've opened that line of communication, what the goal of your interaction is, and how you're going to deliver your message. In this video, we'll watch 3 segments of a presentation created by MIT students. You will analyze the strategy used to develop the message, and hear how and why the presenters chose this strategy. This video is part of the Communication video series. Successful professional communication begins with the ability to analyze situational variables and make strategic decisions. Hi, my name is Joanne Yates, and I'm a Sloan Distinguished Professor of Management and Deputy Dean in the Sloan School of Management at MIT. After watching this video, you should be able to use a strategic approach in order to communicate effectively. This means that you will be able to Analyze your audience, context and purpose Examine an...

PROFESSOR: I think it's time that we got started. I haven't given a problem set out for a couple of days. So I have one that will cover some material that we'll go over with and develop today and some new material that we're not going to introduce for a while. AUDIENCE: [INAUDIBLE]? PROFESSOR: Yes, this is Thursday. And this is for the near future. I've given you two-- two a week before. So it's the adjective you're objecting to not the problem set, of course. Today we're going undertake another major step in our development of three dimensional crystallographic symmetries. We have just completed derivation of the crystallographic point groups, so these are the macroscopic symmetries that crystals can have. And then, by analogy, to what we did in two dimensions, the next step would be to take each of these point groups and hang it at a lattice point of some three dimensional lattice that can accommodate them. We have not as yet developed th...

PROFESSOR: Well, last time Gerry really let the cat out of the bag. He introduced the idea of assignment. Assignment and state. And as we started to see, the implications of introducing assignment and state into the language are absolutely frightening. First of all, the substitution model of evaluation breaks down. And we have to use this much more complicated environment model and this very mechanistic thing with diagrams, even to say what statements in the programming language mean. And that's not a mere technical point. See, it's not that we had this particular substitution model and, well, it doesn't quite work, so we have to do something else. It's that nothing like the substitution model can work. Because suddenly, a variable is not just something that stands for a value. A variable now has to somehow specify a place that holds a value. And the value that's in that place can change. Or for instance, an expression like f of x might have a side eff...