Geometrical Optics

Physics, SSC-KPK Class 10. This chapter is split into 64 topics and has 1,542 practice questions. The topics covered are listed below, followed by 10 free sample questions from the chapter.

Topics in this chapter

1. Laws of reflection 24 questions
2. Uses of curved mirrors 22 questions
3. The lens equation and its derivation 22 questions
4. The camera as an optical instrument 21 questions
5. Magnification numericals for mirrors 25 questions
6. Telescope numericals 27 questions
7. Total internal reflection and the critical angle 25 questions
8. Mirror problems: finding f, d_o or R 27 questions
9. Refraction of light and its terms 23 questions
10. Speed of light in a medium numericals 29 questions
11. Power of a lens numericals 28 questions
12. Critical angle formula and its derivation 20 questions
13. Optical centre, principal axis and focal point of lenses 23 questions
14. Images formed by a convex lens (Example 12.6) 23 questions
15. Image characteristics 25 questions
16. Mirror examples and exercises from the book 24 questions
17. Bending of light: denser and rarer media, glass slab 23 questions
18. Critical angle numericals 27 questions
19. Optical instruments: examples and exercises from the book 22 questions
20. Terms used in reflection of light 23 questions
21. Magnification numericals for lenses 25 questions
22. Table of refractive indices (Table 12.2) 29 questions
23. Snell's law of refraction 22 questions
24. Lens equation numericals: concave lens 24 questions
25. Sign convention for mirrors 23 questions
26. Dispersion of light through a prism 24 questions
27. Centre of curvature, pole and principal axis 24 questions
28. Mirror equation numericals: concave mirror real image 28 questions
29. Lens problems: finding f, d_o or power 27 questions
30. Lens equation numericals: convex lens real images 26 questions
31. The refracting telescope 23 questions
32. Sign convention for lenses and power of a lens 22 questions
33. Lens examples and exercises from the book 21 questions
34. Focal point and focal length of mirrors 25 questions
35. Short-sightedness (myopia) 22 questions
36. The compound microscope 21 questions
37. Ray tracing for spherical mirrors 25 questions
38. Compound microscope numericals 28 questions
39. Refractive index of a medium 22 questions
40. Focal length and radius of curvature numericals 24 questions
41. Snell's law numericals: finding the refractive index 25 questions
42. Images formed by convex and plane mirrors 24 questions
43. Ray tracing for lenses 23 questions
44. Mirror equation numericals: convex mirror 26 questions
45. Mirror equation numericals: virtual image in a concave mirror 25 questions
46. Lenses: convex and concave 25 questions
47. The mirror equation and its derivation 23 questions
48. Angular magnification and the simple microscope 24 questions
49. Resolving power 20 questions
50. Optics and luminous objects 22 questions
51. Structure of the human eye 23 questions
52. Optical fibres 25 questions
53. Refraction examples and exercises from the book 21 questions
54. Snell's law numericals: light entering a denser medium from air 28 questions
55. Spherical mirrors: concave and convex 23 questions
56. Endoscope, red Moon and total internal reflection exercises 21 questions
57. Refraction through a prism and angle of deviation 23 questions
58. Lens equation numericals: magnifying glass (virtual image) 24 questions
59. Accommodation, near point and far point 24 questions
60. Eye defects: lens correction numericals 26 questions
61. Snell's law numericals: between two media 24 questions
62. Long-sightedness (hyperopia) 21 questions
63. Images formed by a concave mirror (Table 12.1) 26 questions
64. Simple microscope numericals 28 questions

Sample questions: Geometrical Optics

10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.

Q1. A concave mirror can form an enlarged image while a convex mirror forms only a reduced one because

• A. a convex mirror absorbs a part of the light that falls on it
• B. a convex mirror is always much smaller in size than a concave one
• C. a concave mirror always has a smaller radius of curvature
• D. a concave mirror converges the rays and can bring them to a nearer focus(correct answer)

Answer: D.Concave mirrors converge parallel rays, so an object inside the focal length gives an enlarged virtual image; convex mirrors only diverge rays, giving reduced images.

Q2. Which ray pair is traced identically for both concave and convex mirrors?

• A. only the A-ray
• B. the A-ray and the F-ray
• C. only the F-ray
• D. the P-ray and the C-ray(correct answer)

Answer: D.P-ray (equal angle to the axis) and C-ray (reflected back on itself) behave the same; the A- and F-rays pass through F only for a concave mirror (or appear to for a convex one).

Q3. As an object is moved from far away toward the focal point of a concave mirror, the real image

• A. moves away from the mirror and becomes larger(correct answer)
• B. moves toward the mirror and becomes smaller
• C. stays at the centre of curvature
• D. stays at the focal point and becomes larger

Answer: A.The image moves from just inside the focal region outward, passing C (same size), and grows larger as the object approaches F (standard consequence of Table 12.1).

Q4. The image formed by a convex mirror can never be received on a screen because

• A. it is inverted
• B. it is enlarged
• C. it is too small
• D. it is virtual(correct answer)

Answer: D.The rays reflected from a convex mirror diverge and only appear to come from a point behind the mirror, so no screen at the image position shows it.

Q5. Drawing accurate ray diagrams to scale is replaced by the mirror equation when

• A. the image position and magnification are needed with precision(correct answer)
• B. only a rough sketch of the image is needed
• C. the mirror is a plane mirror
• D. the object is placed at infinity

Answer: A.The book: to determine the magnification and position precisely it is necessary to draw very accurate scaled diagrams; the mirror equation gives a precise relation.

Q6. Conceptual Question 7 asks whether a nearsighted person wearing glasses can see clearly underwater. A reasonable answer is

From your book: see this page (page 104) Full page Open book

From your book: see this page (page 105) Full page Open book

• A. yes, because water has a lower index than the glass
• B. no, because the lens power in water is much reduced (smaller index difference)(correct answer)
• C. yes, because glasses work equally well everywhere
• D. yes, because water has a larger index than air

Answer: B.A lens bends light because of the index difference between lens and surroundings; glass-to-water differs less than glass-to-air, so the correction largely fails (standard knowledge).

Q7. In arthroscopic surgery an optical fibre cable is used to

• A. shine light on the inside of a joint and carry back the reflected light(correct answer)
• B. cut the bone of the joint with a blade
• C. freeze the tissue of the joint
• D. measure the blood pressure of the patient

Answer: A.The book (Point to Ponder): light is shone onto the internal area of a joint through an optical fibre cable and the reflected light is viewed by the surgeon.

Q8. As an object is moved from far away toward the focal point of a convex lens, its real image

• A. becomes virtual and upright at 2f
• B. moves toward the lens and becomes smaller
• C. stays at the focal point and becomes larger
• D. moves away from the lens and becomes larger(correct answer)

Answer: D.From f (far object) the image distance grows to 2f at dₒ = 2f and then to infinity at dₒ = f; the image grows (standard consequence of Example 12.6).

Q9. Key Points define the telescope as a device meant for viewing distant objects, producing an image that is

• A. larger than the image that can be seen with the unaided eye(correct answer)
• B. always real and formed on a screen
• C. smaller than the image seen with the unaided eye
• D. always upright with respect to the object

Answer: A.Key Points: telescope: device meant for viewing distant objects, producing an image that is larger than the image that can be seen with the unaided eye.

Q10. How does the objective of a telescope differ from that of a microscope?

• A. the telescope objective forms virtual images only
• B. the telescope objective is concave while the microscope objective is convex
• C. the telescope objective has a long focal length, the microscope objective a short one(correct answer)
• D. there is no difference between the two objectives

Answer: C.A telescope objective gathers light from distant objects (fₒ large; 19 m in Example 12.9), whereas the microscope objective needs a short focal length (1.0 cm in Example 12.8).