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Question
The human eye has an approximate angular resolution of `phi` = 5.8 × 10–4 rad and typical photoprinter prints a minimum of 300 dpi (dots per inch, 1 inch = 2.54 cm). At what minimal distance z should a printed page be held so that one does not see the individual dots.
Solution
It is given, angular resolution of the human eye `phi` = 5.8 × 10–4 rad and printer prints 300 dots per inch.
The linear distance between two dots is `l = 2.54/300 cm = 0.84 xx 10^-2 cm`
At a distance of z cm, this subtends an angle `phi = l/z`
∴ `z = 1/phi = (0.84 xx 10^-2 cm)/(5.8 xx 10^-4)` = 14.5 cm
If a printed page be held at a distance of 14.5 cm, then one does not be able to see the individual dots.
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