DISPERSION OF LIGHT AND OPTICAL INSTRUMENTS-I : MCQs & SHORT ANSWERS

MULTIPLE-CHOICE QUESTIONS

*INDEX-TOPIC SEARCH

SELECT THE CORRECT ALTERNATIVE:

1. ________ decomposes white light into its constituent colours.
   
   
   
   1. Flat glass slab
   2. Convex mirror
   3. Convex lens
   4. Prism
      
   
   
   
2. Arranging in the ascending order of wavelength, which one is true ?
   
   
   
   1. Blue,Green,Red
   2. Orange,Green,Red
   3. Blue,Yellow,Green
   4. Orange, Yellow, Green
      
   
   
   
3. The velocity of waves of all colours is same in _______
   
   
   
   1. water
   2. air
   3. vacuum
   4. glass
      
   
   
   
4. In a transparent medium, the velocity of ______ light is the least.
   
   
   
   1. red
   2. green
   3. yellow
   4. violet
      
   
   
   
5. _______ is not a primary colour of white light.
   
   
   
   1. Red
   2. Blue
   3. Violet
   4. Green
      
   
   
   
6. Blue + red = _______
   
   
   
   1. magenta
   2. cyan
   3. yellow
   4. violet
      
   
   
   
7. Blue + green = _______
   
   
   
   1. magenta
   2. cyan
   3. yellow
   4. violet
      
   
   
   
8. Red + green = _______
   
   
   
   1. magenta
   2. cyan
   3. yellow
   4. violet
      
   
   
   
9. Red + green + blue = _______
   
   
   
   1. white
   2. cyan
   3. magenta
   4. black
      
   
   
   
10. Blue + yellow = _______
    
    
    
    1. magenta
    2. red
    3. cyan
    4. white
       
    
    
    
11. Green + magenta = _______
    
    
    
    1. cyan
    2. yellow
    3. red
    4. white
       
    
    
    
12. Red + cyan = _______
    
    
    
    1. white
    2. green
    3. violet
    4. magenta
       
    
    
    
13. Pigments are mixed according to _______ method.
    
    
    
    1. additive
    2. subtractive
    3. multiplicative
    4. fractional
       
    
    
    
14. ________ can vary thickness and hence the focal length of eye-lens.
    
    
    
    1. Retina
    2. Vitreous humour
    3. Cornea
    4. Ciliary muscles
       
    
    
    
15. In the spectrum of white light which colour is deviated maximum /
    
    
    
    1. Red
    2. Yellow
    3. Violet
    4. Blue
       
    
    
    
16. The splitting of white light into seven colours is known as ______
    
    
    
    1. reflection
    2. refraction
    3. interference
    4. dispersion
       
    
    
    
17. In spectrum obtained with prism which colour is deviated maximum ?
    
    
    
    1. Violet
    2. Red
    3. Green
    4. Orange
       
    
    
    
18. Primary colours are :
    
    
    
    1. Red, blue, yellow
    2. Red, orange, yellow
    3. Red, blue, green
    4. Red, green, cyan
       
    
    
    
19. Which of the following is not a primary colour ?
    
    
    
    1. Red
    2. Blue
    3. Green
    4. Yellow
       
    
    
    
20. Primary pigments are :
    
    
    
    1. Yellow, green, magenta
    2. Magenta, yellow, cyan
    3. Blue, green, yellow
    4. Blue, green, violet
       
    
    
    
21. Hypermetropia is caused by...
    
    
    
    1. low converging power of eye lens
    2. low diverging power of eye lens
    3. high converging power of eye lens
    4. retinal displacement
       
    
    

ANSWERS TO MCQs:
(1) D (2) A (3) C (4) D (5) C (6) A (7) B (8) C (9) A (10) D (11) D (12) A (13) B (14) D (15) A (16) D (17) A (18) C (19) D (20) B (21) A

SHORT ANSWERS

1. Rainbow is the evidence of which fact ?
   
   

   ANS:Rainbow is the evidence of the fact that white light is composed of seven colours.

   
   
2. What is spectrum of white light ?
   

   ANS:The colours obtained on screen after the dispersion of white light form a group of bands called 'spectrum of white light'.

   
   
3. Define : Dispersion of light.
   

   ANS:The separation of white light into its constituent colours is called dispersion of light.

   
   
4. Why does dispersion of light occur ?
   

   ANS:Dispersion of light occurs because different colours are refracted in different proportion by the prism.

   
   
5. Which colour of light has maximum velocity while passing through a tarnsparent medium ?
   

   ANS:Red colour of light has maximum velocity while passing through a transparent medium.

   
   
6. What determines the colour of the object ?
   

   ANS:The colour of the light which is reflected from the object determines the colour of the object.

   
   
7. What happens to the light falling on an opaque object ?
   

   ANS:When light is incident on an opaque object, some of its colours are absorbed and some(remaining) colours are reflected from the object.

   
   
8. Why does a green leaf appear green ?
   

   ANS:A green leaf appears green because when white light falls on it, other colours of light are absorbed by the leaf and only the green light is reflected.

   
   
9. Why does a red rose appear black when seen in green light ?
   

   ANS:When green light falls on a red rose, it absorbs all the green light. So no light is reflected from the surface of red rose and it appears black.

   
   
10. Mention the primary colours of white light.
    

    ANS:Red, blue and green are the three primary colours of white light.

    
    
11. Why are red, blue and green called primary colours of white light ?
    

    ANS:Red, blue and green are called primary colours of white light because combination of these three colours produces white light.

    
    
12. What do we mean by composite colours ?
    

    ANS:Colours obtained by the mixing of primary colours are aclled composite colours.

    
    
13. Give examples of composite colours.
    

    ANS:Magenta, cyan and yellow are composite colours.

    
    
14. What are complimentary colours ?
    

    ANS:Any two colours which produce white light on mixing are called complimentary colours.

    
    
15. Give two examples of complimentary colours.
    

    ANS:Blue and yellow; green and magenta are examples of complimentary colours.

    
    
16. How are coloured pictures are produced on T.V. screen ?
    

    ANS:Coloured pictures are produced on T.V. screen by mixing of primary colours of light in various proportions.

    
    
17. If red, blue and green pigments are mixed then white pigment is not obtained.Why ?
    

    ANS:If red, blue and green pigments are mixed then white pigment is not obtained because pigments are mixed according to subtractive method whereas the colours of light are mixed by additive method.

    
    
18. Mention three primary pigments.
    

    ANS:Cyan, magenta and yellow are three primary pigments.

    
    
19. Mention two defects of sight.
    

    ANS:Nearsightedness (myopia) and farsightedness (hypermetropia) are the two defects of sight.

    
    
20. Which defect is caused due to excessive convergence of the light rays ?
    

    ANS:Nearsightedness is caused due to excessive convergence of the light rays.

    
    
21. Which defect is caused due to excessive divergence of the light rays ?
    

    ANS:Farsightedness is caused due to excessive divergence of the light rays.

    
    
22. What type of lens is used to correct the defect of nearsightedness ?
    

    ANS:A concave lens of appropriate focal length is used to correct the defect of nearsightedness(myopia).

    
    
23. What type of lens is used to correct the defect of farsightedness ?
    

    ANS:A convex lens of appropriate focal length is used to correct the defect of farsightedness (hypermetropia).

    
    
24. Mention the principle of simple microscope.
    

    ANS:The principle of simple microscope is that when an object is placed between the optical center and focus of a convex lens; a magnified, erect and virtual image of the object is obtained.

    
    
25. What is a simple microscope ?
    

    ANS:A simple microscope is a convex lens used to get the magnified image of a small object.

    
    
26. What is a compound microscope ?
    

    ANS:An instrument using two convex lenses to obtain the magnified image of a small object is called a compound microscope.

    
    
27. In compound microscope, the focal length of objective lens is smaller than that of the eyepiece. True or false ?
    

    ANS:This is a true statement.

    
    
28. If an object reflects all colours of incident light, what is its colour ?
    

    ANS:If an object reflects all colours of incident light, its colour is white.

    
    
29. If an object absorbs all colours of incident light, what is its colour ?
    

    ANS:If an object absorbs all colours of incident light, its colour is black.

    
    
30. What is the function of ciliary muscles ?
    

    ANS:The function of ciliary muscles is to vary the focal length of the eyelens by changing the thickness of the lens.

    
    
31. When white light is incident on blue pigment which colours of light are reflected from it ?
    

    ANS:When white light is incident on blue pigment; violet, blue and green colours of light are reflected from it.

    
    
32. When white light is incident on yellow pigment which colours of light are reflected from it ?
    

    ANS:When white light is incident on yellow pigment; yellow, orange and green colours of light are reflected from it.

    
    
33. Green colour is absorbed by yellow and blue pigment. True or false ?
    

    ANS:This is a false statement.

    
    
34. If blue and yellow pigments are mixed, then which colour of light will be reflected ?
    

    ANS:If blue and yellow pigments are mixed, then only green colour of light will be reflected.

    
    
35. What type of image with respect to original object is obtained by telescope ?
    

    ANS: Real and inverted image is obtained by telescope with respect to the original object.