Human Eye

General Specifications

Diameter: Approx. 2.3–2.5 cm.
Weight: Approx. 7-8 grams.
Resolution: Roughly 576-megapixel equivalent.
Focusing Mechanism: Accommodating lens (~20 diopters) + Fixed cornea (~40 diopters).
Photoreceptors: Rods (low-light vision) and Cones (color/detail vision).

Parameter	Approximate Value
Eyeball Diameter	\(\sim 24\text{ mm}\) (anteroposterior)
Refractive Power	\(\sim 58.6\text{ dpt}\) (relaxed), \(\sim 70.6\text{ dpt}\) (accommodated)
Focal Length	\(\sim 17.1\text{ mm}\) (relaxed), \(\sim 14.2\text{ mm}\) (accommodated)
Field of View	\(\sim 108^{\circ }\) (maximum)
Pupil Diameter	\(2\text{–}8\text{ mm}\) (regulated by iris)
Blind Spot	\(\sim 1.5\text{ mm}\) wide (15° temporally from fovea)
Eyeball Volume	\(\sim 6.5\text{ mL}\)
Average Weight	\(\sim 7.5\text{ g}\)
Number of Photoreceptors	\(\sim 130\text{ million}\) (rods & cones)
Least Distance of Vision	\(\sim 25\text{ cm}\) (for normal vision)

Component/Feature	Specification
Size/Scale Diameter	6 inches (150 mm) or 7 inches (175 mm/178 mm)
Vernier Reading	1 minute of arc (30 seconds also common)
Main Scale	0-360° with divisions of (0.5 circ ) (150 mm or 175 mm circle)
Vernier Scale	Double ended vernier separated by (180 circ )
Collimator Lens	Achromatic, 178 mm focus, 32 mm clear aperture
Telescope Lens	Achromatic, 178 mm focus, 32 mm clear aperture
Eyepiece	Ramsden Type ((10 times ) or (15 times ) with cross-line graticule
Slit	Unilaterally adjustable, 6mm long
Fine Adjustment	Provided for both telescope and collimator (laterally and vertically)
Prism Table	Marked with lines; leveling screws & interchangeable clamp
Main Structure	Heavy cast metal with bright plated fittings (sometimes stainless steel scale)
Accessories	Prism holder, Grating holder, Watchmaker’s eyeglass, L-key, Hardwood case

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