Question

# Assuming human pupil to have a radius of 0.25 cm and a comfortable viewing distance of 25 cm, the minimum separation between two objects that human eye can resolve at 500 nm wavelength is

Solution

## Assuming human pupil to have a radius r = 0.25 cm or diameter d = 2r = 0.5 cm The wavelength of light is λ = 500 nm = 5 × 10−7 m. sin θ=1.22λd sin θ = 1.22×5×10−70.5×10−2 = 1.22 × 10−4 The distance of comfortable viewing is D = 25 cm = 0.25 m. Let x be the minimum separation between two objects that the human eye can resolve. sin θ = xD D sin θ = 0.25 × 1.22 × 10−4 = 3 × 10−5 m = 30 μm.

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