LIGHT:REFLECTION AND REFRACTION-I:MCQs AND SHORT ANSWERS

MULTIPLE-CHOICE QUESTIONS

*INDEX-TOPIC SEARCH

SELECT THE CORRECT ALTERNATIVE:

1. The speed of light is_______ in vacuum.
   
   
   
   1. 3 x 10⁵ m/s
      
   2. 3 x 10⁸ m/s
      
   3. 3 x 10⁸ km/s
      
   4. 3 x 10⁶ m/s
      
   
   
2. The wavelength of the visible light is ________.
   
   
   
   1. 4 x 10^(-7) to 8 x 10^(-7) m
      
   2. 4 x 10⁷ to 8 x 10⁷ m
      
   3. 4 x 10^(-7) to 8 x 10^(-7) Å
      
   4. 4 x 10⁷ to 8 x 10⁷ Å
      
   
   
3. We can see objects because of_______
   
   
   
   1. reflection
      
   2. refraction
      
   3. transmission
      
   4. diffraction
      
   
   
4. The image formed by a convex mirror is always________
   
   
   
   1. real
      
   2. enlarged
      
   3. virtual and enlarged
      
   4. diminished
      
   
   
5. As you move an object away from a convex mirror, its image becomes_____ and moves towards______
   
   
   
   1. smaller, infinity
      
   2. smaller, focus
      
   3. enlarged, infinity
      
   4. enlarged, focus
      
   
   
6. For a spherical mirror, ______ is true.
   
   
   
   1. f = 2R
      
   2. R = 2f
      
   3. fR = 2
      
   4. fR = 1/2
      
   
   
7. The mirror formula is ________.
   
   
   
   1. 1/u - 1/v = 1/f
      
   2. 1/f + 1/u = 1/v
      
   3. f = uv/(u+v)
      
   4. f = (u+v)/uv
      
   
   
8. For a plane mirror, magnification (m)=________
   
   
   
   1. 0
      
   2. 1
      
   3. ± 1
      
   4. ≤ 0
      
   
   
9. Magnification for convex mirror is ________.
   
   
   
   1. always positive
      
   2. always negative
      
   3. sometimes positive
      
   4. 1
      
   
   
10. The image formed by a concave lens is ________.
    
    
    
    1. always real and enlarged
       
    2. always real and diminished
       
    3. always virtual and enlarged
       
    4. always virtual and diminished
       
    
    
11. The lens formula is ________.
    
    
    
    1. 1/f = 1/u + 1/v
       
    2. 1/f = 1/u - 1/v
       
    3. 1/f = 1/v - 1/u
       
    4. 1/f + 1/v = u
       
    
    
12. 1 diopter = ________.
    
    
    
    1. 1 m
       
    2. 1 m^(-1)
       
    3. 1 cm
       
    4. 1 cm^(-1)
       
    
    
13. Which of the following is a true statement?
    
    
    
    1. The power of a lens is always positive.
       
    2. The power of a lens is always negative.
       
    3. The power of a convex lens is positive.
       
    4. The power of a concave lens is positive.
       
    
    
14. Image formed by a concave mirror is erect and enlarged.What is the position of the object?
    
    
    
    1. Between focus F and the center of curvature
       
    2. At the center of curvature
       
    3. Beyond the center of curvature
       
    4. Between pole and the focus
       
    
    
15. If the focal length of a spherical mirror is 40 cm, then its radius of curvature is _______ cm.
    
    
    
    1. 80
       
    2. 20
       
    3. 10
       
    4. 5
       
    
    
16. The velocity of light in vacuum is _______ ms^(-1)
    
    
    
    1. 3 x 10⁶
       
    2. 3 x 10⁸
       
    3. 3 x 10 ¹²
       
    4. 3 x 10¹⁵
       
    
    
17. If the angle of incidence, θ_i = 0°, the angle of reflection, θ_r = ________.
    
    
    
    1. 0°
       
    2. 90°
       
    3. 180°
       
    4. 45°
       
    
    
18. No matter how far is the object from the mirror, the image of the object appears erect. The mirror is ________.
    
    
    
    1. concave
       
    2. convex
       
    3. either concave or convex
       
    4. none of these
       
    
    
19. A boy is standing at a distance of 2 m in front of a plane mirror.The distance between the boy and his image is ________ m.
    
    
    
    1. 4
       
    2. 3
       
    3. 2
       
    4. 1
       
    
    
20. The image formed by a concave mirror is real, inverted and of the same size as that of the object.The position of the object should be ________.
    
    
    
    1. beyond the center of curvature of mirror
       
    2. between the center of curvature and the focus
       
    3. at the center of curvature of the mirror
       
    4. at the focus
       
    
    
21. Which of the following has the highest refractive index?
    
    
    
    1. Glass
       
    2. Water
       
    3. Pearl
       
    4. Diamond
       
    
    
22. Absolute refractive index of any medium is always _______.
    
    
    
    1. 1
       
    2. > 1
       
    3. < 1
       
    4. 0
       
    
    
23. The image formed by a plane mirror is ______.
    
    
    
    1. real
       
    2. diminished
       
    3. enlarged
       
    4. laterally inverted
       
    
    
24. The incident ray passing through the focus(F) of a mirror ______ after reflection.
    
    
    
    1. passes through C
       
    2. passes through F
       
    3. becomes parallel to the principal axis
       
    4. passes through the pole
       
    
    
25. The incident ray passing through the center of curvature(C) of a mirror ______ after reflection.
    
    
    
    1. passes through C
       
    2. passes through F
       
    3. passes through the pole
       
    4. becomes parallel to the principal axis
       
    
    
26. The incident ray parallel to the principal axis of a mirror ______ after reflection.
    
    
    
    1. passes through C
       
    2. passes through F
       
    3. passes through the pole
       
    4. reverts back in the opposite direction
       
    
    
27. According to the sign convention, the distance of object...
    
    
    
    1. is always positive
       
    2. is always negative
       
    3. may be positive or negative
       
    4. is equal to object height
       
    
    
28. According to the sign convention, the distance of image...
    
    
    
    1. is always positive
       
    2. is always negative
       
    3. may be positive or negative
       
    4. is equal to image height
       
    
    
29. The refractive index of a denser medium with respect to a rarer medium is...
    
    
    
    1. 1
       
    2. greater than 1
       
    3. smaller than 1
       
    4. negative
       
    
    
30. The refractive index of a rarer medium with respect to a denser medium is...
    
    
    
    1. 1
       
    2. greater than 1
       
    3. smaller than 1
       
    4. negative
       
    
    
31. Total internal reflection will occur if the angle of reflection is...
    
    
    
    1. 45°
       
    2. 60°
       
    3. 90°
       
    4. 99°
       
    
    
32. Magnification for ______ image is always ______.
    
    
    
    1. real, positive
       
    2. real, negative
       
    3. virtual, negative
       
    4. any, negative
       
    
    
33. If magnification is +1.5, the image is______.
    
    
    
    1. erect
    2. diminished
    3. real
    4. inverted
       
    
    

ANSWERS TO MCQs:

(1) B (2) A (3) A (4) D (5) B (6) B (7) C (8) B (9) A (10) D (11) C (12) B (13) C (14) D (15) A (16) B (17) A (18) B (19) A (20) C (21) D (22) B (23) D (24) C (25) A (26) B (27) B (28) C (29) B (30) C (31) D (32) B (33) A

SHORT ANSWERS

1. What is light?
   
   

   ANS:Light is an electromagnetic radiation which produces sensation in our eyes.

   
   
2. What is the range of wavelength of visible light in Å units ?
   

   ANS:4000 to 7000 Å
   

   
   
3. Which waves do not require material medium for propagation?
   
   

   ANS: Electromagnetic waves do not require material medium for propagation.

   
   
4. What happens to the speed of light when it passes through a transparent medium?
   
   

   ANS: The speed of light is reduced significantly when it passes through a transparent medium.

   
   
5. What happens to light when it is incident on the surface separating two mediums ?
   

   ANS:A part of the incident light is reflected, a part is transmitted and rest is absorbed.
   

   
   
6. Define: Ray of light.
   

   ANS: A straight line path joining one point to another in the direction of propagation of light is known as a ray.

   
   
7. What is a beam of light?
   

   ANS: A bundle of light rays is called a beam of light.

   
   
8. Which phenomena enable the focusing of light by lens and mirrors?
   

   ANS:Refraction and reflection are the phenomena which enable the focusing of light by lens and mirror.

   
   
9. What is an image?
   

   ANS:Whan a number of rays starting from a point meet at another point after reflection or refraction, the second point is called the image of the first point.

   
   
10. Define: Real image.
    

    ANS:When the rays emerging from one point meet really at another point after reflection or refraction, the image formed is called real image.

    
    
11. What is virtual image?
    

    ANS:When the rays emerging from one point appear to meet, when extended backwards, after reflection or refraction, the image formed is virtual image.

    
    
12. Mention two kinds of reflection.
    

    ANS:Regular reflection and Irregular(diffused) reflection are the two kinds of reflection.

    
    
13. Which type of surfaces produce regular reflection?
    

    ANS:Smooth and highly polished surfaces produce regular reflection.

    
    
14. Which type of surface produces irregular reflection?
    

    ANS:Rough surface produces irregular reflection.

    
    
15. What is 'incident angle'?
    

    ANS:The angle that the incident ray makes with the normal is known as incident angle(or Angle of incidence).

    
    
16. What is 'reflection angle'?
    

    ANS:The angle that the reflected ray makes with the normal is known as reflection angle (or Angle of reflection).

    
    
17. How are curved mirrors formed?
    

    ANS:Curved mirrors are formed by cutting circular cross-section of spherical shell.

    
    
18. Define: Radius of curvature of a mirror.
    

    ANS:The radius of the spherical shell from which the mirror is made is called the radius of curvature of a curved mirror.

    
    
19. Define: Centre of curvature of a mirror.
    

    ANS:The center of the spherical shell from which the mirror is made is called the centre of curvature of the mirror.

    
    
20. Define: Pole of a mirror.
    

    ANS:The centre of the reflecting surface is called pole of the mirror.

    
    
21. What is the Principal axis of mirror?
    

    ANS:The imaginary line passing through the pole and the centre of curvature is called the principal axis of mirror.

    
    
22. Define: Aperture of mirror.
    

    ANS:The diameter of the reflecting surface is called aperture of mirror.

    
    
23. Define:Principal focus of a mirror.
    

    ANS:The point where the rays parallel to the principal axis meet or appear to meet after reflection is called the principal focus of the mirror.

    
    
24. Define:The focal length of mirror.
    

    ANS:The distance between the pole and the principal focus of a mirror is called the focal length of mirror.

    
    
25. What is the position, nature and size of the image formed by a concave mirror when the object is at infinity?
    

    ANS:The image is formed at focus; it is real, inverted and highly diminished.

    
    
26. What is the position, nature and size of the image formed by a concave mirror when the object is beyond the center of curvature of the mirror?
    

    ANS:The image is formed between the focus and the center of curvature; it is real, inverted and diminished.

    
    
27. What is the position, nature and size of the image formed by a concave mirror when the object is at C, the center of curvature of the mirror?
    

    ANS:The image is formed at the center of curvature; it is real, inverted and of the same size as the object.

    
    
28. What is the position, nature and size of the image formed by a concave mirror when the object is between C and F?
    

    ANS:The image is formed beyond C; it is real, inverted and enlarged.

    
    
29. What is the position, nature and size of the image formed by a concave mirror when the object is at F?
    

    ANS:The image is formed at infinite distance; it is real, inverted and highly enlarged.

    
    
30. What is the position, nature and size of the image formed by a concave mirror when the object is between pole and F?
    

    ANS:The image is formed behind the mirror; it is virtual, erect and enlarged.

    
    
31. Define: Magnification.
    

    ANS:The ratio of the height of the image to the height of the object is called magnification.

    
    
32. Define: Refraction.
    

    ANS:The change in the direction of a ray of light when it enters from one transparent medium to another transparent medium is called refraction.

    
    
33. Define: Optical center of a lens.
    

    ANS:Optical center of a lens is the center of lens on the principal axis.

    
    
34. Define: Radius of curvature of lens.
    

    ANS:The radii of spheres whose parts form the lens surfaces are called radii of curvature of lens.

    
    
35. Define: Principal focus of convex lens.
    

    ANS:The point of convergence of the rays parallel to principal axis on the principal axis is called the principal focus of a convex lens.

    
    
36. Define: Focal length of lens.
    

    ANS:The distance between the optical center and the principal focus is called the focal length of lens.

    
    
37. Mention the position, nature and size of the image formed by a convex lens when the object is placed at infinity.
    

    ANS:The image is on the opposite side of the object at focus; it is real, inverted and highly diminished(point sized).

    
    
38. Mention the position, nature and size of the image formed by a convex lens when the object is placed beyond 2F₁.
    

    ANS:The image is between F₂ and 2F₂; it is real, inverted and diminished.

    
    
39. Mention the position, nature and size of the image formed by a convex lens when the object is placed at 2F₁.
    

    ANS:The image is at 2F₂; it is real, inverted and of the same size as the object.

    
    
40. Mention the position, nature and size of the image formed by a convex lens when the object is between F₁ and 2F₁.
    

    ANS:The image is beyond 2F₂; it is real, inverted and enlarged.

    
    
41. Mention the position, nature and size of the image formed by a convex lens when the object is placed at focus F₁.
    

    ANS:The image is at infinite distance; it is real, inverted and highly enlarged.

    
    
42. Mention the position, nature and size of the image formed by a convex lens when the object is placed between focus F₁ and optical center O.
    

    ANS:The image is on the same side of the lens as the object; it is virtual, erect and enlarged.

    
    
43. Define: Power of lens.
    

    ANS:The reciprocal of the focal length(f) of a lens is called the power of that lens.

    
    
44. What is the SI unit of power of lens?
    

    ANS:The SI unit of power of lens is dioptre.

    
    
45. The power of a convex lens is positive.True or false?
    

    ANS:Yes, this is a true statement.

    
    
46. The power of a concave lens is positive.True or false?
    

    ANS:No, this is a false statement.

    
    
47. Which instrument is used to measure the power of a lens?
    

    ANS:Dioptremeter is used to measure the power of a lens.

    
    
48. What is the power of a convex lense whose focal length is 50 cm ?
    

    ANS:(+)2.0 D
    

    
    
49. The power of a lens is (-)4.0 D. What is its focal length in cm ?
    

    ANS:(-)25 cm, the negative sign indicates that the lens is concave.
    

    
    
50. On what does the lateral shift of an emergent ray depend in case of a rectangular glass slab ?
    

    ANS:The lateral shift is proportional to the perpendicular distance between two refracting surfaces of the glass slab.
    

    
    
51. Define: Critical angle.
    

    ANS:The angle of incidence of a ray for which the angle of refraction is 90° is called critical angle.

    
    
52. Define: Total internal reflection.
    

    ANS:When the angle of incidence of a ray is greater than the critical angle, the refracted ray is in the same medium, i.e. the light is totally reflected in the same medium. This is known as total internal reflection.

    
    
53. What happens to a ray of light travelling from optically rarer to optically denser medium?
    

    ANS:The ray of light bends towards the normal.

    
    
54. State Snell's law.
    

    ANS:The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

    
    
55. Which type of waves are light waves?
    

    ANS:Light waves are electromagnetic(non-mechanical)waves.

    
    
56. A medium is necessary for the propagation of light waves.True or false?
    

    ANS:No, this is a false statement.

    
    
57. If incident angle is 40° for a plane mirror, what should be the angle of reflection?
    

    ANS:The angle of reflection should be 40°.

    
    
58. What is the type of mirror having focal length +10 cm?
    

    ANS:The mirror is convex.

    
    
59. Which medium has higher refractive index, glass or water?
    

    ANS:Glass has higher refractive index.

    
    
60. In which medium is the velocity of light higher, glass or water?
    

    ANS:The velocity of light is higher in water.

    
    
61. Give the names of two phenomena occuring due to refraction.
    

    ANS:Twinkling of stars and mirage are the two phenomena occuring due to refraction.

    
    
62. If the focal length of convex lens is 25 cm, what is its power?
    

    ANS:The power of the given convex lens is 4.0 D or +4.0 D.(HINT: p = 1/f where f is in meter)

    
    
63. Which kind of lens has positive power, converging or diverging ?
    

    ANS:A converging lens has positive power.

    
    
64. Mention the unit of refractive index.
    

    ANS:Refractive index is unitless.

    
    
65. Which type of mirror is used as rear-view mirror in vehicles ?
    

    ANS:A convex mirror is used as rear-view mirror in vehicles.

    
    
66. The refractive index of diamond is 2.42. What is the meaning of this statement in relation to the speed of the light ?
    

    ANS:It means that the light travels 2.42 times faster in vacuum than in diamond.