Human Eye — Set 4
Physics · मानव नेत्र · Questions 31–40 of 60
The choroid layer helps vision mainly by?
Correct Answer: C. Preventing internal reflection by absorbing stray light
The choroid is dark and pigmented, so it absorbs scattered light. This reduces internal reflections inside the eyeball. It also contains many blood vessels that nourish eye tissues.
The crystalline lens of the human eye is typically?
Correct Answer: A. Biconvex and transparent
The eye lens is transparent so light can pass through it. Its general shape is biconvex, which helps converge light. Its curvature can change during accommodation.
Most refraction happens at the cornea mainly because?
Correct Answer: C. There is a large refractive index change at the air–cornea boundary
Refraction is stronger when the refractive index changes more at a boundary. Air to cornea has a large index difference, so bending is large. The lens then fine-adjusts focus for different distances.
Hypermetropia is commonly corrected using a?
Correct Answer: A. Convex lens
In hypermetropia, near objects tend to focus behind the retina. A convex lens converges light before it enters the eye. This helps the image form on the retina for near objects.
Presbyopia is mainly caused by?
Correct Answer: B. Reduced accommodation due to aging
The correct answer is 'Reduced accommodation due to aging'. Presbyopia happens when focusing ability decreases with age. The lens becomes less elastic and ciliary muscles may weaken. Reading glasses or bifocals can help restore near vision.
The visual pigment in rod cells is commonly called?
Correct Answer: A. Rhodopsin
Rod cells contain the pigment rhodopsin. Rhodopsin is important for vision in low light. It is sometimes referred to as visual purple.
A person’s near point is 1 m. What power of lens helps them read at 25 cm?
Correct Answer: B. +3 D
To read at 25 cm, the lens should form a virtual image at the near point of 1 m. With u = -0.25 m and v = -1 m, 1/f = 1/v - 1/u = -1 - (-4) = +3. So the required power is +3 D, a convex lens.
Aqueous humor drains mainly into the venous system through the?
Correct Answer: D. Canal of Schlemm
Aqueous humor must be continuously drained to maintain normal pressure. A key drainage route is through the canal of Schlemm. Blocked drainage can contribute to raised intraocular pressure.
In myopia, distant objects appear blurred because their image is formed?
Correct Answer: C. In front of the retina
In myopia, the eye’s optical power is too strong or the eyeball is too long. So rays from distant objects converge before reaching the retina. A concave lens helps shift the focus back to the retina.
In hypermetropia, near objects appear blurred because their image is formed?
Correct Answer: A. Behind the retina
In hypermetropia, the eye’s optical power is insufficient for near objects. So rays from near objects would focus behind the retina. A convex lens provides extra convergence to bring focus onto the retina.