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Class 10 Science: The Human Eye and the Colourful World, 8 practice questions with answers

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These are 8 practice questions on NCERT Class 10 Science Chapter 10, The Human Eye and the Colourful World, each with a short answer and the textbook page it comes from. They cover the iris and pupil, accommodation, the near point, the three refractive defects, a numerical on a corrective lens, and two everyday effects of light (an earlier sunrise and red danger signals). Try each one before you read the answer. Another Class 10 Science set covers how hormones coordinate the body: Control and Coordination.

These questions are our own, drafted with AI help. Every number was re-computed by a test script and every statement was checked against the chapter, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

Parts of the eye and accommodation

Question 1. Which part of the human eye controls the size of the pupil? (Iris; retina; cornea; or optic nerve.)

Answer: the iris. The iris is a dark muscular diaphragm behind the cornea that controls the size of the pupil, and the pupil regulates the amount of light entering the eye. (Page 161.)

Question 2. When you shift your gaze from a distant tree to a book held close to your eyes, what happens to your eye lens?

Answer: the ciliary muscles contract, the lens becomes thicker and its focal length decreases. For nearby objects the curvature of the lens increases; when the muscles are relaxed the lens is thin and its focal length is longer, which lets you see distant objects. The ability of the eye lens to adjust its focal length is called accommodation. (Section 10.1.1, page 162.)

Question 3. What is the near point of a normal eye of a young adult, in cm?

Answer: about 25 cm. The minimum distance at which objects can be seen most distinctly without strain is the near point, or least distance of distinct vision; for a young adult with normal vision it is about 25 cm. (Page 162.)

Defects of vision and their correction

Question 4. Name the three common refractive defects of vision.

Answer: myopia (near-sightedness), hypermetropia (far-sightedness) and presbyopia. They can be corrected with suitable spherical lenses. (Page 162.)

Question 5. In a myopic eye, where is the image of a distant object formed, and which lens corrects the defect? (In front of the retina, convex lens; behind the retina, concave lens; in front of the retina, concave lens; or behind the retina, convex lens.)

Answer: in front of the retina; a concave lens. A concave lens of suitable power brings the image back onto the retina. (Page 163.)

Question 6. A girl's near point is 75 cm, so she cannot read a book held at 25 cm. (a) Name this defect of vision. (b) Where must a lens form the image of the book, and what is the object distance, with signs? (c) What focal length must the lens have? (d) What is its power, in dioptres, to two decimal places, and what kind of lens is it?

Answer: (a) She cannot see near objects clearly: hypermetropia (far-sightedness). (b) The image must form at her near point, so v = −75 cm for an object at u = −25 cm. (c) By the lens formula 1/v − 1/u = 1/f: 1/f = −1/75 + 1/25 = 2/75, so f = 37.5 cm. (d) P = 100 ÷ 37.5 ≈ +2.67 D; f is positive, so it is a convex (converging) lens. (Hypermetropia and its correction by a convex lens, page 163. The lens formula and the power P = 1/f are from Chapter 9, pages 155 and 157; see our Light, Reflection and Refraction questions.)

Light in the atmosphere

Question 7. Because of atmospheric refraction, the Sun is seen about 2 minutes before the actual sunrise and about 2 minutes after the actual sunset. By about how much does this lengthen the daytime we observe, in minutes?

Answer: about 4 minutes. About 2 minutes are gained at sunrise and about 2 minutes at sunset, so the day appears about 2 + 2 = 4 minutes longer. (The textbook gives the two figures, advance sunrise and delayed sunset, page 168; adding them is our step.)

Question 8. Why are "danger" signal lights red in colour? (Red light is scattered the most by fog or smoke; red light has a shorter wavelength than blue light; or red light is scattered the least by fog or smoke.)

Answer: red light is scattered the least by fog or smoke. So it can be seen in the same colour at a distance. (Red light actually has a longer wavelength than blue light, by about 1.8 times.) (Page 169.)

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Sources

All opened and read on 21 October 2026. Page numbers are the printed page numbers of the textbook.

The facts are from the textbook pages above. The questions, worked answers and checks are our own, and every number was re-computed by script. This guide is general information; follow your teacher and the textbook.