Board Previous Year Questions (PYQs)

Board Previous Year Questions (PYQs)

These are exam-style questions arranged by marks. Write answers to the depth suggested by the marks. Diagrams earn marks - always draw and label them where asked.

1-Mark Questions

Q1. Name the part of the eye where the image is formed. (Ans: Retina.)

Q2. What is the least distance of distinct vision for a normal eye? (Ans: About 25 cm.)

Q3. Which lens is used to correct myopia? (Ans: Concave (diverging) lens.)

Q4. Why are danger signals red? (Ans: Red is scattered the least, so it is seen from far even in fog.)

Q5. Name the phenomenon responsible for the twinkling of stars. (Ans: Atmospheric refraction.)

2-Mark Questions

Q6. What is meant by the power of accommodation of the eye? Ans: It is the ability of the eye lens to change its focal length (by the action of the ciliary muscles) so as to focus objects at different distances on the retina. Relaxed muscles → thin lens (large f) for distant objects; contracted muscles → thick lens (small f) for near objects.

Q7. A person cannot see objects beyond 1.2 m. Name the defect and the corrective lens. Ans: The far point (1.2 m) is nearer than infinity → myopia. It is corrected with a concave lens whose power is $P = 1/(-1.2) = -0.83$ D.

Q8. State two causes of myopia. Ans: (i) Excessive curvature of the eye lens (too much converging power); (ii) elongation of the eyeball. Both make the image of a distant object form in front of the retina.

3-Mark Questions

Q9. A person needs a lens of power -5.5 D for distant vision and +1.5 D for near vision. Find the focal length of each lens. (NCERT) Ans: Distant: $f = 1/(-5.5) = -0.182$ m $= -18.2$ cm (concave). Near: $f = 1/(1.5) = 0.667$ m $= +66.7$ cm (convex).

Q10. The far point of a myopic person is 80 cm. Find the nature and power of the lens required. (NCERT) Ans: $v = -0.8$ m, $u = -\infty$; $1/f = -1.25$ m⁻¹ → concave lens, P = -1.25 D.

Q11. Distinguish between myopia and hypermetropia (image position and corrective lens). Ans: In myopia the image of a distant object forms in front of the retina; corrected by a concave lens. In hypermetropia the image of a near object forms behind the retina; corrected by a convex lens.

5-Mark Questions

Q12. (a) Draw a labelled diagram of the human eye. (b) State the function of the cornea, iris, pupil and retina. (c) What is accommodation? Ans: (a) Diagram must show cornea, iris, pupil, ciliary muscles, crystalline lens, retina and optic nerve. (b) Cornea - main refraction of incoming light; iris - controls pupil size; pupil - controls the amount of light entering; retina - light-sensitive screen where the real, inverted image forms. (c) Accommodation is the ability of the eye lens to adjust its focal length to focus objects at different distances.

Q13. (a) What is hypermetropia? Draw ray diagrams of the defect and its correction. (b) The near point of a hypermetropic eye is 1 m. Find the power of the correcting lens (normal near point 25 cm). (NCERT) Ans: (a) Hypermetropia (far-sightedness): near objects' image forms behind the retina; corrected by a convex lens. (b) $u = -0.25$ m, $v = -1$ m → $1/f = -1 + 4 = 3$ → P = +3.0 D (convex).

Q14. Explain with reasons: (i) Why the sky is blue; (ii) Why the Sun appears red at sunrise; (iii) Why stars twinkle but planets do not. Ans: (i) Air molecules scatter shorter (blue) wavelengths more, so the sky looks blue. (ii) At sunrise light crosses a thick atmosphere; blue is scattered away, leaving red. (iii) Stars are distant point sources whose light fluctuates due to atmospheric refraction (twinkle); planets are nearby extended sources whose fluctuations average out (no twinkle).