Question

Lens in man is-
A)Biconvex
B)Spherical
C)Biconcave
D)Cylindrical

Answer 1

Human eye is a sense organ responsible for vision. Eye detects the light and sends the signal to the brain to interpret the final image of an object.

Complete answer:
There are 3 layers in the eye- outermost fibrous tunic, middle vascular tunic layer and innermost retina.
Fibrous tunic consists posteriorly of sclera and anteriorly of cornea. Vascular tunic consists of choroid, ciliary body and iris. Inner layer retina consists of rod and cone cells.
At the anterior side, cornea lies in the outermost region, below cornea lies iris and pupil lies below the iris. Below iris lies a biconvex lens. Pupil controls the amount of light entering the lens.
Aqueous humour is gel like liquid filled between cornea and lens while vitreous humour is filled between the lens and retina. Optic nerve connects the eye to the brain to send and receive signals.
Suspensory ligaments hold the biconvex lens in position and control the change in the focal length of the lens.

Human eye is biconvex so that it can converge the light at a point on the retina.
Spherical lens will have its half as a hollow sphere. Biconcave lens is concave from both the sides and it diverges the light, cylindrical lens light into a line but not into a point. So, all the three types of lenses will not be able to converge the light on the retina.

Hence, the correct answer is option (A)

Note: 1)The focal length of the biconvex lens can be adjusted by suspensory ligaments based on the distance of the object, intensity and color of light.
2)Biconvex lenses are convex from both sides and they converge the light to form an image.