Question

The human eye has a approximate angular resolution of $\varphi =5.8\times {10}^{-4}$ rad and a typical photo printer 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 dies not see the individual dots?

• A. 10 cm
• B. 8.6 cm
• C. 14.5 cm
• D. 29 cm

Answer 1

The correct option is C 14.5 cm

as we Rnow in linch there are 300 dots

$\text{So, in}2.54cm⟶300\text{dots}$

$[$ as $y_{\text{ivch}}=2\cdot 54]$

$\therefore$ Distance between 2 dots $=\frac{2.54}{300}=0.84\times {10}^{-2}cm$

for small $Q;Q=\frac{l}{z};z=\frac{l}{Q}=\frac{0.84\times {10}^{-2}}{5.4\times {10}^{-4}}$

$z=14.5cm$

the minimal distance $z=14.5cm$ irr which the brinted bage held

Hence oftion ' $C$ ) is correct.