Human Eye — Set 3
Physics · मानव नेत्र · Questions 21–30 of 60
Aqueous humor helps the eye mainly by?
Correct Answer: B. Providing nutrients and maintaining pressure
Aqueous humor nourishes the cornea and lens which lack blood vessels. It also helps maintain normal intraocular pressure. Proper pressure supports the shape and function of the eye.
Astigmatism is commonly corrected using a?
Correct Answer: C. Cylindrical lens
Astigmatism occurs due to unequal curvature in different directions. A cylindrical lens provides different power along different axes. This helps focus light properly on the retina.
Color blindness is most commonly caused by a problem with?
Correct Answer: C. Cones
Cones are responsible for color perception. If certain cones are absent or defective, color discrimination becomes difficult. Rods mainly support dim-light vision rather than color.
Persistence of vision in humans is approximately?
Correct Answer: C. 1/16 second
The correct answer is '1/16 second'. The image on the retina remains for a short time after the object is removed. This short retention is called persistence of vision. It helps make rapid sequences of images appear continuous.
The thin membrane that covers the front of the eye (except the cornea) and lines the eyelids is the?
Correct Answer: B. Conjunctiva
The conjunctiva is a thin protective membrane. It covers the sclera and lines the inside of the eyelids. It helps keep the eye moist and reduces friction.
The tough, white outer coat of the human eye is called the?
Correct Answer: C. Sclera
The sclera forms the strong outer layer of the eyeball. It protects the internal parts and maintains shape. The cornea is the transparent front continuation of this outer coat.
Signals from the retina are carried to the brain by the?
Correct Answer: B. Optic nerve
The optic nerve transmits electrical impulses from the retina to the brain. These impulses are interpreted as vision by the visual cortex. Damage to this nerve can reduce or block vision.
Night blindness can be caused by deficiency of?
Correct Answer: A. Vitamin A
Vitamin A is needed to form visual pigments in the retina. Deficiency can reduce rod function and impair dim-light vision. This condition is commonly called night blindness.
For a normal eye, the vergence needed to focus an object at 25 cm is about?
Correct Answer: B. 4 D
Vergence for an object at distance 0.25 m is 1/0.25. This gives 4 diopters as the required converging power. It corresponds to the near point of a normal adult eye.
Which opening mainly controls the amount of light entering the eye?
Correct Answer: D. Pupil
The pupil is the aperture through which light enters the eye. Its size changes to control light entry. The iris muscles adjust this pupil size.