Sunday 10 June 2018

LIGHT 8

Practice Paper
Subject Physics (2019)
Class VIII                           Ch- LIGHT                                     
                                           
1. Name the form of energy which enables us to see the objects? What types of waves are light waves?
2. Define incident ray. reflected ray, normal in the reflection of light,
3. Define a beam of light and a ray of light?
4. Give an example of best reflector of light.
5. State the characteristics of the image formed in  a plane mirror. ?
6. State the characteristics of the image formed  on a cinema screen?
7. An object is placed at a distance of 10 cm in front of a plane mirror. How far would its image be formed?
8. Define angle of reflection and angle of incident. State the law of reflection of light.
9. How can visually challenged persons read and write?
10. Define reflection of light. Name the types of reflection. Which type of reflection leads to the formation of image?
11. (a) If the incident ray strikes the mirror at 90o, what will be the angle of reflection? 
(b) If angle of incident is 30o then what will be the value of angle of reflection? (c) What is the angle of incident of light if the reflected ray is at an angle of 90 deg. to the incident ray ?
12. Differentiate between virtual and real image? What is the nature of image formed by plane mirror?
13. Draw a diagram to show the reflection of light from a plane mirror . Label the following:
(a) Plane mirror  (b) Incident ray 
(c) Reflected ray (d) Point of incidence 
(e) Normal          (f) Angle of incidence 
(g) Angle of reflection.
14. Draw a image  formed by plane mirror  of a point object placed in front of it
15. Name the instrument :
(a) based on multiple reflection used to create new designs and 
(b) which works on reflection of reflected light ? 
(c)  used to split white light into seven colours.
16. What will be the no. of images formed when an object is placed between two (a) parallel plane mirror (b) at 30 deg. 
(c) at 60 deg.                (d) at 90 deg. 
(e) 45 deg                     (f) 120 deg. 
(g) 180 deg.
17. What is the relation between angle of reflection i and angle of reflection r?
18. Define dispersion of light.Give some examples of dispersion of light.
19. Write the names of important parts of eye.What is blind spot?
20. Why the world AMBULANCE is written as its mirror image in front of the hospital vans?
21. What do you mean by lateral inversion? How this phenomenon occurs?
22. What is cataract? How this defect can be removed?
23. Draw a neat and labeled diagram of human eye.
24.Why is it important to take care of our eyes? Mention some activities that may cause damage to our eyes.
25. Write the functions of the following: (a) Optic nerves.(b) Retina.(c) Cornea (d) Pupil (e) Ciliary muscles (f) Retina (g) Eyelids.
26. Draw ray diagram for reflection of incident ray which makes incident angle of 60o
27. How many plane mirror strips are there in a kaleidoscope? What are the uses of kaleidoscope?
28. Define persistence of vision. What is its value?
29.What is the nature of image formed in retina ?
30. Soap bubble is transparent, but seems to be coloured in presence of light. Why?
31. Explain different parts of human eye.
32. The pictures in flip book appears to be moving. Why?
33. What are the common eye defects? Give cure for these defects.
34. State the precautions you will take to protect your eyes?
35. How does our food effects our eye?
36.What are the near and far points of the eye? or What is the range of vision of a normal human eye?
37. How could visually challenged persons read and write?
38. What do you know about the Braille system?
39. What is meant by power of accommodation ?
40. Light appears white. Why? What are constituent colours of light?
41. Name the colours in the order they appear in the spectrum of sunlight.
42. What is colour blindness? Give reason for this defects.
43. What is short sightedness or Myopia ? How is it correct?
44. What is long sightedness or hypermetropia ? How is it correct?
45. What are cones and rods in the retina of the eye ? What are their functions ? or Which are sensitive to bright light and dim light ?
46. How is night blindness caused?
47. Draw diagrams to show defective eye its correction.
48. Explain how we perceive objects as they are ?
49. Which cells are responsible for viewing in dim light and help in colour vision?
50. Match the following:
        Column 1                                  Column 2
a) Range of vision                           i.long sightedness
b) Short sightedness                       ii.emergent Ray
c) Braille system                            iii.dispersion
d) lower speed of light                    iv. concave lens
e). Ray coming out of glass slab      v. Iris
f). Splitting of white light                vi.visually challenged person
g). Diverging lens                           vii.25 cm to infinity
h). Colour of human eye                 viii. Infinity
i). Hypermetropia                           ix. higher optical density
j). Far point of eye                          x. myopia

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