7. Human Eye and Colourful world

1. The least distance of the distinct vision is about ______ cm.

2. The maximum angle, at which we are able to see the whole object is called ___________.

3. The angle of vision for a healthy human being is about .

4. Iris has a small hole in it called __________.

5. The distance between the lens and retina is about _______ cm.

6. The eye-lens forms a _________ and _________ image of an object on the retina.

7. The retina is a delicate membrane, which contains about 125 million receptors called ‘rods’ and ‘cones’ which receive the _____________.

8. In a receptors of eye rods identify the colour and cones-identify the _____________.

9. The maximum focal length of the eye lens is ______ Cm.

10. The minimum focal length of the eye lens is ______ Cm.

11. The ability of eye-lens to change its focal length is called “_______________”.

12. Some people cannot see objects at long distances but can see nearby objects clearly. This type of defect in vision is called ‘__________’.

13. The defect, in which people cannot see objects beyond far point, is called ‘_________’.

14. Myopia is also called _____________.

15. The least distance of distinct vision, the eye lens can form an image on the retina. This distance is called ‘_________’.

16. The point of maximum distance at which the eye lens can form an image on the retina is called ‘_________’.

17. If we can correct myopia then we need to select ____________.

18. Hypermetropia is also known as “___________”.

19. A person with __________ can see distant objects clearly but cannot see objects at near distances.

20. The minimum focal length of eye lens for the person of hypermetropia is greater than __________ cm.

21. The point of minimum distance at which the eye lens can form an image on the retina is called _________(d).

22. To correct the defect of hypermetropia, we need to use a ______________.

23. __________ is vision defect when the ability of accommodation of the eye usually decreases with ageing.

24. To correct this type of defect of vision we need __________ which are formed using both concave and convex lenses.

25. The degree of convergence or divergence of light rays that can be achieved by a lens is expressed in terms of its ________.