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Smallest Angular Separation

  1. Nov 12, 2015 #1
    1. The problem statement, all variables and given/known data
    For an eye in which the pupil has a radius of 3.0 mm, what is the smallest angular separation that can be resolved when two violet (λ = 400 nm) objects are placed side by side?

    2. Relevant equations
    theta_r = sin(theta_r) = 1.22(wavelength/d)

    3. The attempt at a solution
    theta_r = 1.22(400*(.000000001)) / (6*.001) = .0000813

    This is incorrect. Where have I gone wrong?
  2. jcsd
  3. Nov 12, 2015 #2


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    Who says it's not correct ? I get what you get using that formula.

    When I Google angular resolution and look at the picture , then violet at 6 mm aperture shows something that looks around 15 arcsec, and sure enough 8.13 x 10-5 * 180/##\pi## = 17/3600 .

    My eyes sure don't dissolve two spots on a 10 m far wall that are 0.8 mm apart, but perhaps that isn't the idea anyway...

    [edit] another contribution: Hyperphysics mentions 2 x 10-4 radians for "Most acute vision, optimum circumstances" -- within a factor 2 of the physical limits imposed by diffraction.

    The only thing I can think of that would spoil the fun is that blue and violet are difficult colours for human eyes, but I don't have anything quantitative on that.
    Last edited: Nov 12, 2015
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