CBSE Class 10 Science Chapter 10 The Human Eye and the Colourful World — 20 MCQs with Answers

The human eye is a natural optical instrument. Light enters through the transparent cornea, passes the pupil (controlled by the iris), and is focused by the crystalline lens onto the retina. The ciliary muscles adjust lens curvature—a process called accommodation—to focus objects at varying distances. The retina contains light-sensitive cells that convert images into electrical signals sent to the brain via the optic nerve. The least distance of distinct vision for a normal eye is about 25 cm (near point), and the far point is at infinity. CBSE papers often ask about the role of each part, accommodation, or the power of the lens. These four MCQs test foundational recall and application of eye anatomy.

Myopia (near-sightedness) occurs when the eyeball is elongated or the lens is too curved, causing distant images to form before the retina. A concave lens diverges rays before they enter the eye, shifting the image back onto the retina. Hypermetropia (far-sightedness) arises when the eyeball is too short or lens power is insufficient; nearby objects focus behind the retina, corrected by a convex lens. Presbyopia is an age-related loss of accommodation due to weakening ciliary muscles and lens rigidity, corrected by bifocal lenses. CBSE Class 10 board papers in 2024 and 2025 featured at least one MCQ and one short question on defect correction. Master the sign convention and lens type for each defect.

Dispersion is the phenomenon of splitting white light into its seven constituent colours (VIBGYOR) when it passes through a prism. It occurs because different wavelengths refract by different amounts—violet has the shortest wavelength and bends the most, red has the longest and bends the least. The band of colours is called a spectrum. Newton demonstrated that white light is composed of multiple colours and that a second inverted prism can recombine them. CBSE frequently asks why violet deviates more or the order of colours. These MCQs test conceptual clarity on refractive index, wavelength, and deviation.

Atmospheric refraction is the bending of light rays as they pass through layers of air with varying densities and refractive indices. It causes the twinkling of stars: starlight bends continuously due to turbulent air, so the apparent position fluctuates. Planets do not twinkle much because they are extended sources, and the averaged effect cancels fluctuations. Atmospheric refraction also makes the Sun visible about two minutes before actual sunrise and after actual sunset, and it causes the apparent flattening of the Sun at the horizon. CBSE board papers have tested these concepts through MCQs and short questions in 2023 and 2024.

Scattering of light is the phenomenon where light rays deviate from their straight path due to collision with particles or molecules. Rayleigh scattering states that intensity of scattered light is inversely proportional to the fourth power of wavelength. Blue light (shorter wavelength) scatters much more than red light (longer wavelength). Therefore, the sky appears blue during the day because sunlight passes through a shorter atmospheric path and blue is scattered into our line of sight. At sunrise and sunset, sunlight travels a longer path; blue and green are scattered away, leaving red and orange, so the Sun and sky appear reddish. The 2025 CBSE sample paper included an assertion-reason question on scattering.

CBSE introduced assertion-reason (A-R) type MCQs from 2020 onward. Each question has two statements: an assertion and a reason. Students must determine if both are true, if the reason correctly explains the assertion, or if one is false. These MCQs test deeper understanding and the ability to link concepts. Chapter 10 lends itself well to A-R questions on defects, scattering, and atmospheric refraction. Higher-order thinking skill (HOTS) questions require application of multiple concepts—for instance, calculating lens power, explaining everyday phenomena, or comparing refractive indices. Practice these formats because they carry higher marks and differentiate top performers.

CBSE Class 10 Science papers typically carry 20 MCQs of 1 mark each in Section A. Chapter 10 contributes 2–3 MCQs covering eye defects, dispersion, scattering, or atmospheric refraction. Negative marking does not apply in CBSE board exams, so never leave an MCQ unattempted. Read the question stem carefully; keywords like 'not', 'except', or 'maximum' change the answer. Eliminate obviously wrong options first—this raises your probability of guessing correctly. For assertion-reason MCQs, evaluate the assertion independently, then the reason, and finally check if the reason logically explains the assertion. Time management is crucial: aim to finish all 20 MCQs in 15–18 minutes, leaving time for numerical and long-answer sections. Mark tricky questions and revisit them if time permits. Practice with previous years' board papers (2020–2025) to familiarise yourself with question phrasing and difficulty levels.

Mistakes in this chapter often stem from conceptual overlap between dispersion and scattering, or misunderstanding sign conventions for lens power. Many students confuse myopia with hypermetropia because both involve the image not forming on the retina—always remember myopia = concave (diverging), hypermetropia = convex (converging). Another frequent error is stating that planets twinkle; they do not, because they are extended sources. Students also mix up 'advanced sunrise' and 'delayed sunset', forgetting both occur due to atmospheric refraction. Assertion-reason MCQs trip up learners who do not verify if the reason truly explains the assertion. Finally, numerical slip-ups happen when converting focal length from cm to m or forgetting the sign (concave is negative power). Reviewing these pitfalls before the exam can easily add 2–3 marks.

NCERT Class 10 Science Chapter 10 includes in-text questions, end-of-chapter exercises, and numerical problems on lens power and focal length. Solving these reinforces MCQ concepts because board paper MCQs are often reworded NCERT questions. For instance, NCERT asks 'Why do stars twinkle?'—expect an MCQ or assertion-reason variant. Numerical problems like calculating power from focal length appear as one-mark MCQs with four computed options. CBSETUTOR.ai users can upload photos of NCERT exercise problems and get instant step-by-step solutions, clarifying doubts before attempting MCQ mock tests. Interleaving MCQ practice with NCERT exercises cements both recall and application, a proven strategy to boost board exam scores by 10–15 percent.

As board exams approach, focus on high-yield facts and formulae. Memorise the structure of the eye (cornea, iris, lens, retina, optic nerve) and the function of each part. Know the three defects: myopia (concave lens, far point nearer), hypermetropia (convex lens, near point farther), presbyopia (bifocal lens). Recall the seven colours of the spectrum in order—VIBGYOR—and that violet deviates and scatters most. For atmospheric refraction, remember the key phenomena: twinkling of stars, advanced sunrise, delayed sunset. For scattering, blue sky during the day, red Sun at sunrise/sunset. Revise the formula P=1/f(m) and sign conventions. Make a one-page summary with bullet points and diagrams; review it daily in the week before the exam. Consistent short bursts of revision outperform last-minute cramming.