Question

When dots are placed on a page from a laser printer, they must be close enough so that you do not see the individual dots of ink. To do this, the separation of the dots must be less than Raleigh's criterion. Take the pupil of the eye to be 3.5 mm and the distance from the paper to the eye of 48 cm; find the maximum separation (in cm) of two dots such that they cannot be resolved. (Assume the average wavelength of visible light is 555 nm.)

Answer 1

Answer:

273 dots/inch

Explanation:

We are given:

•Average wavelength = 555mm

•d = 3.5mm

• distance = 48cm

Let's use the Reyleigh formula:

∅ = 1.22$\frac{wavelength}{D}$

Substituting figures in the formula, we have:

$\frac{(1.22)(555mm[\frac{10^-9m}{1mm}])}{3.5mm[\frac{10^-^3}{1mm}]}$

$1.935*10^-^4 rad$

From the formula above, we get:

∅ = x/d

where x is distance btw dots and pupil

Solving for x we get:

x =∅d

$x = (1.935*10^-^4 rad)(48)$

$x = 9.3*10^-^3cm$

To calculate dots per inch(dpi), we use:

$dpi = \frac{2.54cm/inch}{x}$

We already know 1 inch =2.54cm

Therefore,

$dpi = \frac{2.54cm/inch}{9.3*10^-^3cm}$

273 dots/inch