PHY 242 Final Exam on 12/15/99 at (ughh) 8 am

The final exam is scheduled for 8 to 11 am on Wed, Dec 15 in room CA310. You will have a full three hours for the exam should you need it. The exam will consist of 12 to 14 problems and will be comprehensive. About half of the exam questions will be from the material covered since Exam III. Since we will not have separate exam for this portion of the course, this will give all material equal weight.

If you have a conflict see me immediately!

A few sample problems for the last section (material since Exam III) can be found below. And now, for the usual warnings and disclaimers.

You are responsible for all material covered in previous exams and quizzes. DO NOT ASSUME that a subject not covered in the sample exam below will not show up on the final exam! During the exam, you will be provided with an equation sheet. You will be allowed to use only the equations on the sheet, or others that you derive from those on the sheet. I would suggest that you create your own equation sheet from the equations in the summary at the end of each chapter and use only that when trying the problems below. Resist the temptation to simply look for a similar problem in the text or notes (the standard "get the homework done" technique). That will better prepare you for the exam.

Help Session will start at 9:30 am on Tuesday. We will meet in the lab.

Sample Physics 242 Final Exam

1. Below is the intensity pattern for a double-slit barrier with slit separation 1500 nm. Sketch and label the intensity patterns for
   a) a double slit with separation 3000 nm.
   b) a single-slit barrier with slit width 1500 nm.
   c) a diffraction grating with 667 lines/mm.

   

2. A train sounds its horn while in a tunnel of width 20 ft. The horn can be heard clearly in front of the tunnel, but is nearly inaudible at an angle of 40^o from directly in front. What is the wavelength of the sound coming from the horn?

3. A spaceship passes earth traveling at .943c (94.3% of the speed of light) towards the Andromeda galaxy.
   a) If the proper length of the ship is 100 m, what length do the earthlings measure for the ship's length?
   b) Relative to the planet Altaire 5, the earth is moving at speed .943c towards the Andromeda galaxy. What is the speed of the spaceship relative to Altaire 5?

   

4. Monochromatic light of wavelength 310 nm strikes a metal that has threshold wavelength 620 nm. What is the maximum speed of the photoelectrons ejected from the metal's surface?

5. What is the wavelength of the lowest energy photons in the Paschen spectral series (n = 3) for the hydrogen spectrum? Is this line visible?

6. You are reviewing a grant proposal to build an electron microscope. In the proposal, the electron beam is created using a 500 V accelerating potential. The proposal claims the microscope is to be used to image bacteria that are about 20 microns in diameter. Is the proposal feasible? Explain.