The human eye has an approximate angular resolution of `phi = 5.8xx10^(-4)` rad and a typical photo printer prints a minimum of 300 dpi (dots per inch, `= 2.54 cm`). Aminimum distance 'z' should a printed page be held so that one doesnot see the indivdual dots is ______ .

Options

A. 14.5 cm
B. 20.5 cm
C. 29.5 cm
D. 28 cm

Answer

A

Explanation

Here, angular resolution of human eye,
`phi=5.8xx10^(-4)`rad
The linear distance between two successive dots in a typical photoprinter is `l=(2.54)/(300)cm=0.84xx10^(-2)cm.`
At a distance of z cm, the gap distance `l` will subtend an angle
`phi=(l)/(z) :. z=(l)/(phi)=(0.84xx10^(-2)cm)/(5.8xx10^(-4))=14.5cm`