Question

A paper, with two marks having separation d, is held normal
to the line of sight of an observer at a distance of 50m. The
diameter of the eye-lens of the observer is 2 mm. Which of
the following is the least value of d, so that the marks can be
seen as separate ? (The mean wavelength of visible light
may be taken as 5000 Å)
(a) 1.25 m (b) 12.5 cm (c) 1.25 cm (d) 2.5 mm

Answer 1

Answer:

(b) 12.5 cm

Explanation:

Here Diameter of eye lens is 2mm

Distance is 50m

Angular limit of eyes resolution is q

diameter of eye lens is given by d

Wavelength given here is A=5000 Å=5*

Ф=Y/D

λ/d=Y/D

Y=λD/d

since diameter is 2mm=2* 10-³

Y=5*10^{-7}*50/2*10^{-3}

Y=12.5*10^{-3}meters

Y=12.5 centimeters

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