1.Draw a neat, labelled diagram of the human eye. Label cornea, iris, pupil, crystalline lens, ciliary muscles, retina, yellow spot, blind spot, and optic nerve.
2.State the specific functions of the following parts of the human eye:
- Cornea
- Iris and Pupil (pupil regulation)
- Crystalline Lens
- Ciliary Muscles
- Retina
3.Define power of accommodation of the human eye. Explain how the curvature and focal length of the eye lens are altered when looking at: (a) distant objects, (b) nearby objects.
4.What is the near point (least distance of distinct vision) and far point of a normal human eye? Explain why holding a book too close to the eye causes strain.
5.What is a cataract? Explain how a cataract develops in old age and how it is medically treated to restore clear vision.
6.Explain why we cannot see objects clearly for a few moments when we enter a dark room from bright sunlight. What physiological change occurs in our iris?
7.What is myopia (short-sightedness)? State two common causes of myopia. Where is the image of a distant object formed in a myopic eye?
8.Show with neat ray diagrams: (a) a myopic eye, (b) the correction of myopia using a suitable spherical lens.
9.A myopic person's far point has decreased to $80\text{ cm}$. Find the nature and power of the corrective lens required to restore normal distant vision.
10.What is hypermetropia (long-sightedness)? State two common causes of hypermetropia. Where is the image of a nearby object formed in an uncorrected hypermetropic eye?
11.Show with neat ray diagrams: (a) a hypermetropic eye, (b) the correction of hypermetropia using a suitable spherical lens.
12.The near point of a hypermetropic eye is $1\text{ m}$. Find the nature and power of the lens required to read a book comfortably at a normal distance of $25\text{ cm}$.
13.What is presbyopia? Explain its causes in elderly individuals. How does presbyopia differ from hypermetropia? How is it corrected using bifocal lenses?
14.Differentiate between myopia and hypermetropia based on: (a) symptoms, (b) image position, (c) causes, and (d) corrective lens.
15.What is astigmatism? (Brief conceptual introduction). How does it affect vision, and which specialized lens is used to correct it?
16.Draw a neat, labelled ray diagram showing the refraction of a ray of light through a triangular glass prism. Label the incident ray, refracted ray, emergent ray, angle of incidence ($i$), angle of refraction ($r$), angle of emergence ($e$), angle of prism ($A$), and angle of deviation ($D$).
17.Define angle of deviation ($D$) of a prism. Discuss how the angle of deviation changes with the angle of incidence (briefly outline the $i\text{--}D$ curve).
18.What is dispersion of white light? Explain the cause of dispersion when white light passes through a glass prism in terms of wavelength and speed.
19.Name the seven constituent colours of white light in order of their increasing frequency. Which colour bends the most, and which colour bends the least? Explain why.
20.Describe Sir Isaac Newton's classic experiment using two identical glass prisms (one erect, one inverted) to prove that white light is made of seven constituent colours and cannot be split further (recombination of spectrum).
21.How is a rainbow formed in nature? Explain the three sequential optical phenomena (refraction, dispersion, total internal reflection, refraction) that water droplets perform in the sky. Draw a neat ray diagram showing rainbow formation.
22.Why is a rainbow always observed in the opposite direction of the sun? Explain the geometry of observation.
28.What is scattering of light? How does scattering differ from refraction and reflection?
29.What is the Tyndall Effect? State two daily-life observations where the Tyndall effect is clearly visible.
30.State Rayleigh's Law of Scattering. Explain why short wavelengths (blue/violet) are scattered much more intensely than long wavelengths (red/orange) by fine air molecules.
31.Why does the clear sky appear blue during a bright sunny day? Why does it not appear violet, even though violet has an even shorter wavelength than blue?
32.Why does the sky appear pitch black and dark to an astronaut in deep space or a passenger flying at extremely high altitudes?
33.Why are danger signal lights universally red? Explain in terms of scattering by dust and smoke particles.
34.Explain why the sun appears deep red at sunrise and sunset, but white when it is directly overhead at noon. Draw a neat ray diagram showing the distance of atmosphere traversed.
35.Why do clouds appear white? Explain in terms of the size of water droplets relative to the wavelength of light.
Rohan is a Class 10 student. He sits on the very last bench of his classroom and struggles to read the writing on the blackboard clearly, experiencing mild headaches. However, he can easily read his science textbook when held at a normal distance. The school doctor diagnoses him with a common defect of vision.
36.Based on Case Study 1, answer the following:
- Identify Rohan's defect of vision. State two common physiological causes of this defect.
- Where is the far point of Rohan's eye situated compared to a normal eye?
- Draw ray diagrams showing Rohan's eye defect and its correction using a suitable lens.
Grandfather is 62 years old. He loves reading newspapers, but lately, he has to hold the paper at arm's length (about 60 cm away) to read the print clearly. He also complains that threading a needle has become nearly impossible. The eye specialist prescribes spectacles with progressive or bifocal lenses.
37.Based on Case Study 2, answer the following:
- Identify the two distinct eye defects Grandfather is likely suffering from.
- Explain the physiological reasons behind these defects in old age (mention ciliary muscles and eye lens flexibility).
- How does a bifocal lens work? Which part (upper or lower) corrects distant vision, and which corrects near reading vision?
In a physics lab, Kavita passes a narrow beam of white light from a carbon arc lamp through a triangular glass prism placed on a white sheet. On a screen placed on the other side, she observes a beautiful, multi-coloured band. She measures that the violet light has bent significantly more than the red light.
38.Based on Case Study 3, answer the following:
- Name the optical phenomenon demonstrated by Kavita. What is the multi-coloured band on the screen called?
- Explain why different constituent colours of white light deviate by different angles when passing through the glass prism. (Reference their speed inside glass).
- If Kavita places a second identical glass prism in an inverted position next to the first one, what will be observed on the screen?
A science documentary shows footage from a NASA Mars rover showing that during a Martian dust storm, the daytime sky appears reddish-butterscotch, and sunsets appear blue. This is opposite to what we experience on Earth. The narrator mentions that Martian dust particles are relatively large and iron-rich.
39.Based on Case Study 4, answer the following:
- What determines which wavelength of light is scattered more by a planet's atmosphere?
- Why does Mars show a reddish sky during dust storms in terms of dust particle size?
- Discuss how the lack of a thick atmosphere on the Moon affects the colour of the lunar sky for astronauts.
A person with a defective eye can read a book placed at $25\text{ cm}$ only if he uses spectacles of power -2.0 D. Another person can read the same book only if she uses spectacles of power +2.5 D. The students are asked to evaluate their near points and far points.
40.Based on the Spectacle Power Case, answer the following:
- Identify the defects of vision of both individuals based on their spectacle powers.
- Calculate the focal lengths of the lenses used by both persons.
- Determine which person cannot see distant objects clearly, and which cannot see nearby objects.
A mystery beam 'B' of light is passed through a liquid containing suspended colloidal sulphur particles. An observer looking at the liquid from the side sees a bluish glow. An observer looking at the beam directly from the exit end sees a deep orange-red spot.
41.Based on the puzzle description, answer the following:
- Identify the optical phenomenon occurring inside the liquid. What is this effect called?
- Why does the sideways observer see a blue glow while the direct observer sees a red spot? Explain based on scattering.
- Write down the chemical equation for the reaction used to produce colloidal sulphur in a lab (sodium thiosulphate + hydrochloric acid).
42.State the function of the iris and pupil. How do they coordinate to act as a variable aperture diaphragm, regulating the entry of light in dim vs bright light?
43.Why is the human eye lens a double convex lens of varying thickness rather than a rigid glass lens? Explain the biological advantage.
44.Explain what is meant by persistence of vision. How is this property exploited in cinematography and motion pictures to create the illusion of smooth movement?
45.Why do we have two eyes for vision instead of just one? List two distinct advantages of binocular (two-eyed) vision in terms of field of view and depth perception.
46.A student sitting on the front bench cannot see the writing on the blackboard clearly. What is the eye defect of this student? How is it corrected?
47.Explain why a hypermetropic person's eye lens has a focal length that is too long or the eyeball has become too short. How does a convex lens correct this?
48.Calculate the focal length and power of the lens required for a person whose near point is $50\text{ cm}$ to read a book at $25\text{ cm}$.
49.Why does the apparent position of a star fluctuate continuously? Explain how atmospheric turbulence and convective air currents affect refractive index.
50.Why does the sun appear flat and oval at the horizon during sunrise and sunset, but perfectly circular at noon? Explain based on the gradient of atmospheric refraction.
51.Explain why the path of a light beam is not visible when passed through a true solution (like salt water), but becomes highly visible when passed through a colloidal solution (like milk).
52.Differentiate between dispersion of light and scattering of light based on the optical mechanisms and the medium involved.
53.Explain the formation of a secondary rainbow. Why is a secondary rainbow fainter, and why are its colours inverted compared to a primary rainbow? (Brief conceptual overview).
54.A person needs a corrective lens of power -4.5 D for distant vision. For his near vision, he needs a lens of power +1.5 D. Find the focal lengths of both lenses.
55.Why does the sky appear red at sunset but blue at noon? Draw a neat ray diagram showing the relative thickness of Earth's atmosphere traversed in both cases.
56.What is presbyopia? Why is it also called "old-age hypermetropia"? Can a person suffer from both myopia and presbyopia simultaneously? Explain.
57.Describe the role of the retina as a light-sensitive screen. Discuss the functions of: (a) Rod cells (black & white, dim light), (b) Cone cells (colour vision, bright light).
58.Why do stars twinkle but the Moon and planets do not? Explain in terms of point source vs extended source of light.
59.What is the angle of deviation in a prism? Discuss how the angle of deviation depends on: (a) angle of incidence, (b) refractive index of the prism material, (c) angle of the prism.
60.A myopic person's far point is $50\text{ cm}$. Find the power of the concave lens he needs to view stars clearly.
← Back to Practice Arena