Refraction of Light – CBSE Class 10
1. Refraction of light is
A) Bending of light at a surface
B) Reflection of light
C) Dispersion of light
D) Scattering of light
Answer: Bending of light at a surface
2. Refractive index of a medium is
A) Ratio of speed of light in vacuum to that in medium
B) Ratio of speed of light in medium to vacuum
C) Reciprocal of speed
D) None of these
Answer: Ratio of speed of light in vacuum to that in medium
3. Light bends towards the normal when it passes from
A) Optically rarer to denser medium
B) Optically denser to rarer medium
C) Vacuum to air
D) Air to vacuum
Answer: Optically rarer to denser medium
4. Light bends away from the normal when it passes from
A) Rarer to denser medium
B) Denser to rarer medium
C) Air to glass
D) Vacuum to water
Answer: Denser to rarer medium
5. Laws of refraction were given by
A) Newton
B) Fermat
C) Snell
D) Huygens
Answer: Snell
6. Snell’s law states that
A) sin i / sin r = constant
B) i = r
C) i + r = 90°
D) None of these
Answer: sin i / sin r = constant
7. The constant in Snell’s law is
A) Speed of light
B) Refractive index
C) Wavelength
D) Frequency
Answer: Refractive index
8. Refractive index of air is approximately
A) 1
B) 1.33
C) 1.5
D) 0.33
Answer: 1
9. Refractive index of water is approximately
A) 1
B) 1.33
C) 1.5
D) 1.66
Answer: 1.33
10. Refractive index of glass is approximately
A) 1
B) 1.33
C) 1.5
D) 1.66
Answer: 1.5
11. The speed of light decreases in
A) Denser medium
B) Rarer medium
C) Vacuum
D) Air
Answer: Denser medium
12. Critical angle is
A) Angle of incidence for total reflection
B) Angle of refraction = 0°
C) Both A and B
D) None
Answer: Both A and B
13. Total internal reflection occurs when
A) Light moves from denser to rarer medium and i > critical angle
B) Light moves from rarer to denser medium
C) Light is incident normally
D) Angle of refraction < 0
Answer: Light moves from denser to rarer medium and i > critical angle
14. Critical angle for water-air interface is approximately
A) 42°
B) 48°
C) 60°
D) 90°
Answer: 48°
15. Optical fibre works on the principle of
A) Reflection
B) Refraction
C) Total internal reflection
D) Dispersion
Answer: Total internal reflection
16. Refraction of light through prism causes
A) Reflection
B) Dispersion
C) Total internal reflection
D) Diffraction
Answer: Dispersion
17. Angle of deviation in prism is minimum when
A) Incident ray perpendicular
B) Prism in minimum deviation position
C) Incident ray along base
D) Incident ray along height
Answer: Prism in minimum deviation position
18. Refractive index depends on
A) Wavelength of light
B) Temperature
C) Both A and B
D) None
Answer: Both A and B
19. Convex lens converges light because
A) It is thicker at middle
B) It is thinner at middle
C) It is plane
D) None
Answer: It is thicker at middle
20. Concave lens diverges light because
A) Thicker at edges
B) Thinner at edges
C) Plane
D) None
Answer: Thinner at middle
21. Refractive index is ratio of
A) Speed in medium / speed in vacuum
B) Speed in vacuum / speed in medium
C) Angle of incidence / angle of refraction
D) None
Answer: Speed in vacuum / speed in medium
22. Lens maker’s formula is
A) 1/f = (μ – 1)(1/R1 – 1/R2)
B) 1/f = (μ – 1)(R1 – R2)
C) 1/f = R1 + R2
D) f = R1 R2
Answer: 1/f = (μ – 1)(1/R1 – 1/R2)
23. Refractive index of diamond is approximately
A) 2.42
B) 1.33
C) 1.5
D) 2.0
Answer: 2.42
24. Lateral displacement occurs when
A) Light passes obliquely through slab
B) Light strikes normally
C) Light is reflected
D) Light is dispersed
Answer: Light passes obliquely through slab
25. Light bends towards normal in
A) Denser medium
B) Rarer medium
C) Vacuum
D) Air
Answer: Denser medium
26. Light bends away from normal in
A) Denser medium
B) Rarer medium
C) Vacuum
D) Glass
Answer: Rarer medium
27. Critical angle for glass-air interface is approximately
A) 42°
B) 48°
C) 60°
D) 90°
Answer: 42°
28. Total internal reflection cannot occur in
A) Air-water interface
B) Water-air interface
C) Glass-air interface
D) Diamond-air interface
Answer: Air-water interface
29. Optical fibre diameter is of the order of
A) Few mm
B) Few cm
C) Few μm
D) Few m
Answer: Few μm
30. Optical fibre is used in
A) Telephone cables
B) Endoscopy
C) Internet
D) All of these
Answer: All of these
31. Speed of light in glass is approximately
A) 3 × 10⁸ m/s
B) 2 × 10⁸ m/s
C) 1 × 10⁸ m/s
D) 3.5 × 10⁸ m/s
Answer: 2 × 10⁸ m/s
32. Refraction occurs due to
A) Change in speed
B) Change in direction
C) Both A and B
D) None
Answer: Both A and B
33. Convex lens forms real image when
A) Object beyond focus
B) Object at focus
C) Object between focus and lens
D) Object at infinity
Answer: Object beyond focus
34. Convex lens forms virtual image when
A) Object beyond focus
B) Object at focus
C) Object between focus and lens
D) Object at infinity
Answer: Object between focus and lens
35. Focal length of concave lens is
A) Positive
B) Negative
C) Zero
D) Infinite
Answer: Negative
36. Magnification by concave lens is
A) Positive
B) Negative
C) Zero
D) Infinite
Answer: Positive
37. Light undergoes minimum deviation in prism when
A) Prism tilted
B) Angle of incidence = angle of emergence
C) Prism rotated
D) None
Answer: Angle of incidence = angle of emergence
38. Critical angle increases when
A) Refractive index increases
B) Refractive index decreases
C) Light intensity increases
D) None
Answer: Refractive index decreases
39. Refractive index is always
A) Greater than 1
B) Less than 1
C) Equal to 1
D) Zero
Answer: Greater than 1
40. Ray of light bends more when
A) Speed difference is large
B) Speed difference is small
C) Incident angle = 0
D) All cases
Answer: Speed difference is large
41. Apparent depth of an object decreases when
A) Refractive index of medium increases
B) Refractive index decreases
C) Object moved down
D) None
Answer: Refractive index decreases
42. Light does not bend when
A) Incident ray normal to surface
B) Angle of incidence = 90°
C) Angle of refraction = 0°
D) Both A and C
Answer: Both A and C
43. Ray of light emerging from denser to rarer medium at critical angle
A) Travels along interface
B) Bends into rarer medium
C) Bends into denser medium
D) Gets absorbed
Answer: Travels along interface
44. Maximum total internal reflection occurs in
A) Diamond-air
B) Glass-air
C) Water-air
D) Air-water
Answer: Diamond-air
45. Refractive index μ = sin i / sin r. Here i is
A) Angle of incidence
B) Angle of refraction
C) Critical angle
D) Deviation angle
Answer: Angle of incidence
46. Refractive index μ = sin i / sin r. Here r is
A) Angle of refraction
B) Angle of incidence
C) Critical angle
D) Deviation angle
Answer: Angle of refraction
47. A concave lens always forms
A) Real image
B) Virtual, erect, diminished image
C) Magnified, inverted image
D) None
Answer: Virtual, erect, diminished image
48. Prism disperses light because
A) Refractive index depends on wavelength
B) Speed is constant
C) Incident angle = 0
D) None
Answer: Refractive index depends on wavelength
49. Light travels fastest in
A) Glass
B) Water
C) Air
D) Diamond
Answer: Air
50. Light travels slowest in
A) Air
B) Water
C) Glass
D) Diamond
Answer: Diamond
Also Read: Reflection of Light by Curved Surfaces – CBSE Class 10