Name the following:

(i) Place of best vision in the retina of the eye __________________

(ii) Place of no vision in the retina of the eye __________________

(iii) Kind of retinal cells sensitive to dim light __________________

(iv) The circular opening enclosed by iris __________________

(v) The fibers which collectively hold the lens in position __________________

(vi) The capacity of the eye to focus at different distances __________________

(vii) The kind of lens required to correct nearsightedness __________________

(viii) The layer of the wall of the eye-ball that corresponds to the black lining of the box of a camera __________________

(i) Yellow Spot

Explanation: This particular spot lies at the back of the eye at the center on the horizontal axis of the eyeball contains a maximum number of sense cells, the cones in particular. This results in this region having the brightest vision.

(ii) Blind Spot

Explanation: There are no sensory cells in this particular region of the eye and hence, the point of no vision. The nerve fibres from all sensitive cells of retina converge and bundle together to leave eyeball from this spot.

(iii) Rods

Explanation: The rod cells are sensitive to dim light because they contain a pigment called rhodopsin which are sensitive to dim light.

(iv) Pupil

Explanation: The opening of the iris. The pupil may appear to open (dilate) and close (constrict), but it is really the iris that is the prime mover by its movements.

(v) Suspensory ligaments

Explanation: Muscles are connected to the lens by suspensory ligaments. They adjust the shape of the lens to make it more or less curved, so as to increase or decrease the refraction of light.

(vi) Accommodation

Explanation: Accommodation is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. Accommodation acts like a reflex, but can also be consciously controlled.

(vii) Concave lens

Explanation: Since the nature of the problem of nearsightedness is that the light is focused in front of the retina, a diverging lens (or concave lens) will serve to diverge light before it reaches the eye. This light will then be converted by the cornea and lens to produce an image on the retina.

(viii) Choroid layer

Explanation: The uncontrolled reflection of light from dark choroid produces the photographic red-eye effect on photos.