Human Eye — Set 5
Physics · मानव नेत्र · Questions 41–50 of 60
The light-sensitive cells in the retina are mainly?
Correct Answer: A. Rods and cones
Rods and cones detect light and start the visual signal. They convert light into electrical impulses in the retina. Other retinal neurons then relay these signals toward the optic nerve.
The point of maximum visual acuity in the human eye is the?
Correct Answer: B. Fovea centralis
The fovea centralis is the central region of the retina used for sharp vision. It has a very high concentration of cones for fine detail. That is why direct gaze gives the clearest view.
Rhodopsin is mainly associated with?
Correct Answer: B. Rod cells for dim-light vision
Rhodopsin is the visual pigment found in rods. It helps rods respond well in low light. This is why rods are important for night vision.
The eye lens is mainly held in position by?
Correct Answer: A. Suspensory ligaments (zonules)
The lens is suspended by fine fibers called suspensory ligaments. These fibers connect the lens to the ciliary body. Changes in their tension help the lens change shape during accommodation.
For viewing distant objects, the ciliary muscles generally?
Correct Answer: B. Relax to make the lens thinner
For distant vision, the lens needs a longer focal length. Ciliary muscles relax, reducing the lens curvature and making it thinner. This helps parallel rays focus on the retina.
For viewing nearby objects, the eye lens becomes more convex mainly because?
Correct Answer: B. Ciliary muscles contract and reduce ligament tension
Near objects need more converging power to focus on the retina. Ciliary muscles contract and the lens becomes more curved. This increases lens power and shortens focal length.
The total optical power of a normal human eye (cornea + lens) is approximately?
Correct Answer: D. 60 D
The eye’s optical system has a fairly high converging power. A commonly used approximate value is about 60 diopters. The cornea provides most of this power and the lens fine-tunes it.
The cornea is normally transparent and is generally described as?
Correct Answer: A. Avascular and very sensitive
The cornea has no blood vessels, so it stays clear. It contains many nerve endings, so it is very sensitive. Oxygen for it largely comes from the air through tears.
The middle, vascular, and pigmented coat of the eye is the?
Correct Answer: C. Choroid
The choroid lies between the sclera and the retina. It has many blood vessels that nourish the eye. Its pigment also reduces internal light reflection.
Aqueous humor is mainly produced by the?
Correct Answer: B. Ciliary body (ciliary processes)
Aqueous humor is secreted mainly by the ciliary processes. It circulates through the front chambers of the eye. Its production and drainage help maintain normal eye pressure.