1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Resolving Power and diffraction

  1. Apr 11, 2007 #1
    1. The problem statement, all variables and given/known dataLate one night on a highway, a car speeds by you and fades into the distance. Under these conditions the pupils of your eyes (average refractive index = 1.36) have diameters of about 7.0 mm. The taillights of this car are separated by a distance of 1.3 m and emit red light (wavelength = 660 nm in vacuum). How far away from you is this car when its taillights appear to merge into a single spot of light because of the effects of diffraction?

    2. Relevant equations
    Rayleigh criterion for resolution: theta min = 1.22 (lambda/D)

    3. The attempt at a solution

    lambda eye = lambda vacuum/ n eye
    (660x10^-9m) / 1.32 = 5x10^-7m

    1.22(lambda eye/D)=s/r
    1.22(5x10^-7m)/0.007m = 1.3m/r
    r = 15385 meters
    What am i doing wrong here??
    Last edited: Apr 11, 2007
  2. jcsd
  3. Apr 11, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    the answer should be?
  4. Apr 11, 2007 #3
    the only thing i can think of is:
    a^2 + b^2 = c^2

    (15385m^2) - (.65m^2 ) = answer .....i got 15384.99 which i know isn't right
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook