The Human Eye and the Colourful World
Fill in the blanks
1. The transparent spherical membrane covering the front of the eye is called ____________.
2. _______ is the surface which acts as screen and image is formed on it.
3. The coloured diaphragm between cornea and lens is known as __________.
4. A small hole in iris which controls the intensity of light entering the eye is called __________.
5. ____________ muscles hold the position of the lens and adjust its thickness.
6. The point on retina at which optic nerve leaves the eye is called ___________. At this point if any image formed is not sent to the brain.
7. A point on retina which has highest concentration of sensitive cells and forms a clear image when we see any object minutely, is called __________.
8. The ability of eye lens to focus near and far objects clearly on retina by adjusting is focal length is called the _______________ of the eye.
9. For a young human adult with normal vision, the near point is about ___________ and it is denoted by ______.
10. For a young human adult with normal vision, the far point is at __________.
11. To see objects with both eyes together is called _________ vision.
12. A transparent alkaline liquid between cornea and lens is called ___________. It helps in ________ of light rays in cornea.
13. A jelly fluid filling the space between lens and retina is called _________. It with stands atmospheric pressure and prevents eye ball from collapsing.
14. Human is made up of ___________ jelly fluid material and it is a _________ __________ lens.
15. In __________ distant objects are not clearly visible. It is corrected by using ________ lens.
16. In ___________ objects nearby are not distinctly visible. It is corrected by using _______ lens.
17. ________ occurs due to weakening of ciliary muscles in old age. It can be corrected by using __________ lenses.
18. Power of a spherical lens is the reciprocal value of its _______________.
6: Blind Spot
7: Macula or yellow spot.
9: 25 cm, D
10: infinity (∞)
12: aqueous humour, refraction
13: vitreous humour
14: crystalline, double, convex
15: myopia, concave
16: hypermetropia, convex
17: Presbyopia, bi-focal
18: focal length