Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 26.55
[20 points.] Reflection high-energy electron diffraction2 is a technique where electrons with a kinetic energy of up to 100,000 eV probe the atomic structure of crystalline surfaces. How fast do these electrons travel, as measured from a stationary reference frame? Express your answer as a factor of c. Show your work and explain your reasoning.
Solution and grading rubric:
- p = 20/20:
- r = 16/20:
Nearly correct, but includes minor math errors.
- t = 12/20:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors.
- v = 8/20:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
- x = 4/20:
Implementation of ideas, but credit given for effort rather than merit.
- y = 2/20:
Irrelevant discussion/effectively blank.
- z = 0/20:
p: 6 students
r: 1 students
t: 0 students
v: 2 students
x: 0 students
y: 0 students
z: 1 student
A sample "p" response (from student 1010), although the final result is expressed as a factor of c, "m/s" units are inserted: