ME/CS 132a, Winter 2010, Homework 1 FAQ

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Problem 1

  • It looks like the units don't exactly cancel out in the exponential term in the Planck's law. Is this supposed to happen?
    • Answer: If you are using the old slides from lecture 2, the correct unit for the Planck constant is J·s, or W·s<html>2</html> (but everything else is correct). The revised version has corrected this typo. [Shuo]

Problem 2

Problem 3

  • Do we have to show that the focal length is equal to R/2/(n-1)?
    • Answer: No, you don't. [Shuo]
  • Can we use the fact that the index of refraction of a vacuum (and approximately the index of refraction of air) is 1?
    • Answer: You can assume that the refractive index of the air is 1 when deriving the thin lens equation, but the first part (showing the ray is not refracted if it passes the center of a thin lens) shouldn't depend on this. [Shuo]

Problem 4