PHY 242 Final Exam on 12/17/98
... It's the FINAL EXAM, but REMAIN CALM!
The final exam is scheduled for 10:30 to 12:30 on Thursday, Dec 17 in room CA310. However, 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.
A few sample problems from a previous final exam (1992) 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. If you can't solve the problems, come see me. And don't wait until the night before the exam!!
Sample Physics 242 Final Exam
- Two very large conducting plates, separated by 50 cm, are connected to a 12 V car battery as shown. A 1 gm pith ball floats suspended between the plates. Find the electric field between by the plates and find the charge on the ball. (a FBD is recommended!)
- A solid conducting sphere carries a total charge of +2Q and a concentric conducting shell carries total charge -3Q. Indicate how the charge is distributed and sketch the electric field lines. Watch relative proportions.
- a) Write down all the equations neccessary to solve for the currents (label them in the diagram) as a function of time in the circuit below.
b) What are the current values a long time after the switch is thrown?
- A magnet is dropped at time t = 0 through a conducting loop. The magnet is exactly half way through the loop at time tm. Sketch the current in the loop vs time. Pay attention to ± directions and to the fact that the magnet is accelerating. (Recall that this was a Puzzle problem this semester!)
- Sketch in the diagram below and describe the forces exerted on the horizontal wire by the vertical wire. Both wires are very long and carry current I as shown.
- A vertical wire with current I has a semicircular segment of radius R in a plane perpendicular to the rest of the wire. Find the magnetic field at the center of the semicircular segment. Use symmetry arguments where appropriate.
- A thin soap film (n = 1.2) varies in thickness from 80 nm to 100 nm. What is the range of wavelengths seen from reflected light? Identify the colors of the two extremes.
- 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.
Polarizing sunglasses have very little effect on light reflected from a vertical window. Briefly explain.
- 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?
- Monochromatic light of wavelength 310 nm strikes a metal that has threshold wavelength 620 nm. What is the smallest deBroglie wavelength possible for the photoelectrons ejected from the metal's surface?
- Using the Bohr model of hydrogen, predict the spectral emission formula for singly ionized helium. Compare the two spectra.