Early Quantum Theory

ASSIGNMENT 5

So in week 5 we increase of scrutiny of the physical world by drawing our attention to the world of atoms and the study of quantum theory. Since ancient times people how thought about what "things" were made of and from. From the ancient Chinese to Aristotle, from Democritus to Niels Bohr to modern day electron cloud theories. We will not go as far back as ancient Greece, but will will instead begin with how physicists in the early 20th century began to "model" what they believed the atom looked like, the experiments that supported it and the revelation that physical reality on the atomic level is quite different than anyone expected it to be then and even now.

 So here we go with the problems for the Week 5 assignment. All discussion posts will go in the Week 5 assignment forum for that week. Subsequent weeks will go in their respective week forum slots. Thanks. Some things to remember when setting up your solutions: 1) Be sure to check your units so that they are all compatible. Example, you may find some units in grams or kilograms while you find other entities in meters/sec or km/sec. Choose what units you are required to answer in or if not required what units you choose. The system of MKS is the standard in the course, but that does not mean the problems are given as mixture like cm/s and kg. 2) Double check that your conversions are correct and that you did not make an error by using dimensional analysis in the calculations. Seconds never will equal kilometers for instance. Although I do not weigh this type of error heavily, I want you to use what I call the "Bungler Alarm" which is to sit back and review your answer and see if it makes sense. Example, if a problem was involving a small distance in cm, you would not expect your conversions to bring you hundreds of miles, unless, of course you were asked to find a really big distance. 3) I have already solved all the problems as well as reviewed the answer key provided to me from the university. I check if there are mistakes including if any constants were used incorrectly. This BTW is why I mentioned you should not waste time and search for similar problems on the web. Many times the mistake was not caught and the error in the calculation just propagates. YOU have the ability to do these problems if you read the slides, read the textbook and participate in the discussions. You also have me. That is why I am here, to bring a warm blooded venue to online teaching. AND I WILL BE THERE TO HELP YOU to understand the material and to understand what it is you are being asked to solve. Just ask and you shall receive.

Question for week 5  - Basically, the question is asking you to explore and explain the differences one would observe in the particle (or corpuscular) model and the wave theory model of light. It is VERY important to remember what exactly a model is. A model is a picture that helps you see in your mind what something might actually me, or in the very least something you make up to see to better understand the phenomenon.  See ATP for a link to a great website that compares and reviews particle vs. wave theory models. There are demos there for you to observe as well. 

Problem Assignment for week 5 -   Problem 1  should read 27 degrees  C not 270 degrees C.   Problem 4  - Remember longest wavelength means smallest frequency. Essentially, you are barely seeing the electron leave the metal.  Problem 7  - There are TWO transitions here. First from n = 5 to n = 2, and then from n = 2 to n = 1. You will discover that only ONE of those transitions result in a visible wavelength, the other is from the Lyman series or far UV part of the spectrum.