1. When a ray of light approaches a smooth polished surface and bounces back, it is called
Answer: C. reflection
Physics Class 10 Unit 14: Optics MCQs
80 multiple choice questions with the correct answer for each. Tap an option to check yourself, or switch on "Show all answers". This is page 1 of 2.
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2. The line perpendicular to the reflecting surface at the point of incidence is called the
Answer: B. normal
3. The first law of reflection states that the incident ray, the reflected ray and the normal
Answer: D. all lie in the same plane
4. The second law of reflection states that the angle of incidence
Answer: A. is equal to the angle of reflection
5. An incident ray makes an angle of 45° with a plane mirror. The angle of reflection is
Answer: D. 45°
6. A ray of light strikes a plane mirror at an angle of 47° with the surface. The angle between the incident and reflected rays is
Answer: C. 86°
7. The image formed by a plane mirror is always
Answer: B. virtual and erect
8. The image formed by a plane mirror is
Answer: A. the same size as the object
9. In a plane mirror, the distance of the image from the mirror is
Answer: A. equal to the distance of the object from the mirror
10. A virtual image
Answer: C. cannot be projected on a screen
11. Refraction of light is the change in
Answer: D. direction of light as it passes from one medium to another
12. The speed of light in vacuum is
Answer: B. 3×108 m/s
13. The speed of light in matter is
Answer: A. less than that in vacuum
14. Light bends towards the normal when it
Answer: B. slows down on entering a denser medium
15. Light bends away from the normal when it
Answer: D. speeds up on entering a rarer medium
16. Refractive index of a medium is defined as
Answer: C. speed of light in vacuum divided by speed of light in the medium
17. The formula for refractive index is
Answer: B. n = c/v
18. The refractive index of any medium cannot be
Answer: C. less than 1
19. The speed of light in diamond (n = 2.419) is about
Answer: A. 1.24×108 m/s
20. The speed of light in a medium of refractive index 1.7 is about
Answer: D. 1.76×108 m/s
21. The speed of light in diamond if its refractive index is 2.5 is
Answer: D. 1.2×108 m/s
22. Snell's law is expressed as
Answer: A. n₁ sin θ₁ = n₂ sin θ₂
23. The refractive index of a medium into which light enters from air at 37° and is refracted at 21° is about
Answer: C. 1.68
24. If light enters a medium at right angles to the boundary, the angle of refraction is
Answer: B. 0°
25. A glass slab dipped in a liquid of the same refractive index shows no boundary because refraction is
Answer: D. zero
26. The apparent flattening of the Sun at dawn and dusk is due to
Answer: A. refraction
27. A ray travelling in a medium of index 1.6 enters at 21° into a medium of index 1.7. The angle of refraction is about
Answer: C. 19.7°
28. The angle of incidence in the denser medium for which the angle of refraction is 90° is called the
Answer: B. critical angle
29. Total internal reflection occurs when light travels from a
Answer: A. denser medium to a rarer medium at an angle greater than the critical angle
30. Total internal reflection can occur only when light travels from
Answer: B. a denser to a rarer medium
31. The formula for the critical angle is
Answer: D. sin θc = 1/n
32. The critical angle of polystyrene (n = 1.49) surrounded by air is
Answer: C. 42.2°
33. The critical angle for light travelling from a medium of index 1.63 into a medium of index 1.35 is about
Answer: D. 55.9°
34. When the angle of incidence equals the critical angle, the refracted ray
Answer: C. moves along the boundary
35. The working principle of optical fibres is
Answer: A. total internal reflection
36. The mirage on a road in summer is explained by
Answer: B. total internal reflection
37. An advantage of optical fibres over copper cables is
Answer: D. higher bandwidth and faster speed
38. A converging lens is also called a
Answer: C. convex lens
39. A converging lens is
Answer: B. thicker at the centre and thinner at the edges
40. The focal length of a converging lens is
Answer: A. positive
41. The focal point of a concave lens is
Answer: A. virtual
42. The image formed by a convex lens for an object at infinity is
Answer: C. real, at the focus and highly diminished
43. An object placed beyond 2F of a convex lens forms an image that is
Answer: B. real, inverted and smaller, between F and 2F
44. An object placed at 2F of a convex lens forms an image that is
Answer: D. real, inverted and the same size at 2F
45. An object placed between F and 2F of a convex lens forms an image that is
Answer: C. real, inverted and larger, beyond 2F
46. An object placed inside F of a convex lens forms an image that is
Answer: B. virtual, erect and enlarged
47. The image formed by a diverging lens for an object at infinity is
Answer: D. virtual, upright and diminished
48. Linear magnification is also equal to
Answer: A. q/p
49. An object of height 2 cm is placed 6 cm from a lens with magnification 3. The image height is
Answer: D. 6 cm
50. An object of height 2 cm is placed 6 cm from a lens with magnification 3. The image distance is
Answer: A. 18 cm
About Physics Class 10 Unit 14 MCQs (Federal Board)
These 80 Physics MCQs cover Class 10 Unit 14: Optics of the Federal Board (FBISE) SSC-II (Class 10) syllabus. They are SLO-based MCQs as per the new pattern for FBISE exams. Each question has four options and the correct answer is shown, so you can practise for the annual examination and find the topics you still need to revise. The questions are split over 2 pages of 50. You can also read the Optics notes for this chapter. Download the Optics MCQs as a PDF using the button at the top of this page.