CBSE Class 10 Science The Human Eye and the Colourful World VBQs Set 04

This page has 14 value-based and competency-based questions with answers for CBSE Class 10 Science Chapter 10, The Human Eye and the Colourful World, drawn from question banks and board-style practice. The questions link the chapter to real life, such as laser surgery, cataract, eye donation, screen time, helping a short-sighted classmate and why there is no rainbow on Mars, and each answer also names the values involved.

Value Based Questions

Question 1. Babin was diagnosed with a long sight problem. He was advised to wear lenses, but he was worried that wearing lenses needs utmost care in his busy schedule. What would you suggest to Babin other than the use of lenses?
Answer:
Babin has hypermetropia (long-sightedness), which is normally corrected by convex lenses.
Instead of spectacles or contact lenses, I would suggest that he consult an eye specialist about laser eye surgery. It reshapes the cornea and can correct common vision problems, reducing the need for lenses. It should be done only after a proper check-up and doctor's advice.
I would also tell him that caring for his eyes and getting regular check-ups is part of looking after his health.
In simple words: Babin should ask an eye doctor about laser surgery instead of lenses.

Teacher's Note:
1. Name the defect and its usual correction first.
2. Values: awareness of health and respect for medical advice.

Question 2. Richie's grandmother was affected by cataract, in which the crystalline lens became a hard cloudy substance. Though the doctor advised traditional cataract surgery, Richie wants something better, in which his grandmother should not suffer a lot and which is done carefully and precisely. As a young medico student, what would you opt for?
Answer:
Cataract is the clouding of the eye lens, which cannot be corrected by spectacles. It is cured by surgery in which the cloudy lens is replaced by an artificial lens.
I would suggest that Richie ask the surgeon about laser-assisted cataract surgery, in which the hard cloudy lens is broken up using a laser and very precise cuts are made in less time.
The final choice should be made with the doctor's advice, and Richie should take care of his grandmother before and after the operation.
In simple words: Laser-assisted surgery can be a quick, precise way to replace a cloudy lens, with the doctor's advice.

Teacher's Note:
1. Explain what cataract is before giving advice.
2. Values: care for the elderly and trust in medical science.

Question 3. What would be your suggestion to your grandfather who is suffering from both the eye defects, hypermetropia and myopia?
Answer:
Myopia is near-sightedness and hypermetropia is far-sightedness.
A person who has both defects is advised to wear spectacles with bifocal lenses. The upper part is a concave lens, which corrects distant vision, and the lower part is a convex lens, which corrects near vision (reading).
I would also take him for regular eye check-ups.
In simple words: Bifocal spectacles have a concave upper part for far and a convex lower part for near.

Teacher's Note:
1. Concave on top, convex at the bottom.
2. Values: care and concern for the elders in the family.

Question 4. John has undergone all medication, including wearing spectacles, lenses and laser treatment. None of the treatments helped him recover his eyesight. What would be your suggestion to overcome his problem?
Answer:
If the problem is a damaged or cloudy cornea, he can be advised to undergo a corneal transplant after consulting an eye specialist.
In this operation the entire eye is not replaced; only the diseased cornea is replaced by the cornea of a donor.
This is possible only because people pledge their eyes. So I would also encourage people around me to donate their eyes.
In simple words: A corneal transplant, made possible by eye donors, may restore sight.

Teacher's Note:
1. Only the cornea is transplanted.
2. Values: gratitude to donors and promoting eye donation.

Question 5. In today's digital world, every human spends around a minimum of eight hours with digital electronic items, which makes the eyes strain more and causes many eye problems. What would be your medical suggestion to reduce the stress and strain caused to the eyes?
Answer:
Long viewing of a nearby screen keeps the ciliary muscles contracted, which causes tired and dry eyes, headaches and blurred vision.
Suggestions: (1) take a break every 20 minutes and look at a faraway object for a few seconds; (2) keep the screen at a comfortable distance and reduce glare, for example with an anti-glare screen or lenses; (3) blink often and do regular eye exercises; (4) sleep well, spend time outdoors and get the eyes tested regularly.
In simple words: Give the eyes regular breaks and cut the glare.

Teacher's Note:
1. Close focus keeps the ciliary muscles strained.
2. Give practical habits.

Question 6. Zia has been suggested by the doctor to avoid blue light to her eyes, which is emitted from all digital items. But in today's world the day does not finish without the use of digital items. What preventive measures would you give to your friend?
Answer:
Blue light is emitted strongly by screens and artificial lighting, and too much exposure, especially at night, can tire the eyes and disturb sleep.
Preventive measures: (1) use a blue-light filter or night mode on phones and computers; (2) reduce the screen brightness and avoid screens just before sleep; (3) take regular breaks and look at faraway objects; (4) use anti-glare or blue-light filtering lenses if the doctor advises.
In simple words: Use night-mode filters, lower the brightness and take breaks from the screen.

Teacher's Note:
1. Give two or three simple, practical measures.
2. Values: self-discipline and health awareness.

Question 7. Varun, instead of copying from the blackboard, used to copy regularly from the notebook of his friend Sudhir, with whom he sat on the same desk. Sudhir told the teacher about it. The teacher asked Varun to get his eyes checked by a doctor and explained to the whole class the reason why Varun copied from Sudhir's notebook. (A) What, in your view, is wrong with Varun's eyes and how can it be corrected? (B) If the doctor prescribes Varun to use lenses of power −0.5 D, what is the type of the lenses? (C) Write the values displayed by Sudhir and his teacher.
Answer:
(A) Varun can read nearby objects (his friend's notebook) but cannot see the distant blackboard, so he has myopia. It is corrected with a concave lens of suitable power.
(B) A negative power means a concave lens. Its focal length is f = 1/(−0.5) = −2 m.
(C) Sudhir showed concern and helpfulness; the teacher showed care and knowledge, and spread awareness in the class.
In simple words: Varun is short-sighted; a concave lens of −0.5 D will help, and his friend and teacher acted caringly.

Teacher's Note:
1. Link the symptom to the defect.
2. Values: concern, helpfulness, awareness.

Question 8. Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles in old age. What type of lenses are required by the persons suffering from this defect to see the objects clearly? Akshay, sitting in the last row in his class, could not see clearly the words written on the blackboard. When the teacher noticed it, he announced that any student sitting in the front row could volunteer to exchange his seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send a message to Akshay's parents advising them to get his eyesight checked. (a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect? (b) State the values displayed by the teacher and Salman. (c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman?
Answer:
Importance of ciliary muscles: they change the curvature of the eye lens and so change its focal length, which lets the eye focus on near and distant objects.
Defect in old age: presbyopia. It is corrected by convex lenses, or bifocal lenses if myopia is also present.
(a) Akshay has myopia. A concave lens is used to correct it.
(b) The teacher showed care, concern and responsibility; Salman showed kindness, helpfulness and willingness to sacrifice his comfort.
(c) Akshay can thank them sincerely, follow the doctor's advice, and help others in need in the same way.
In simple words: Akshay is short-sighted, and the teacher and Salman behaved caringly.

Teacher's Note:
1. Answer each part separately.
2. Values should be specific to what each person did.

Question 9. Millions of people of the developing countries of the world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organised a campaign in your neighbourhood to create awareness about this fact. If you are asked to participate in this mission, how would you contribute in this noble cause? (a) State the objective of organising such campaigns. (b) List two arguments which you would give to motivate the people to donate their eyes after death. (c) List two values which are developed in the persons who actively participate and contribute in such programmes.
Answer:
(a) The objective is to make people aware that corneal blindness can be cured by corneal transplant and to encourage them to pledge their eyes after death.
(b) (i) One donor's two corneas can give sight to two blind persons. (ii) After death the eyes are of no use to the donor, but they can give a person the chance to see the world again; the donation costs nothing and is a noble act.
(c) Social responsibility and compassion (also awareness and cooperation).
In simple words: Eye donation after death can give sight to people with damaged corneas.

Teacher's Note:
1. The cornea is the part that is transplanted.
2. Give two clear arguments and two values.

Question 10. Do you know that corneal impairment can be cured by replacing the defective cornea with the cornea of a donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
Answer:
How: we can form groups of students and volunteers, tie up with an eye bank, hold awareness rallies, speak in schools, colonies and markets, put up posters and share the pledge forms.
Why: many people are blind only because of a damaged cornea. A donated cornea can restore their sight, and only a small number of donors come forward, so awareness is needed.
In simple words: Groups help to spread the message so that more people pledge their eyes.

Teacher's Note:
1. Mention both the method and the reason.
2. Values: social responsibility and teamwork.

Question 11. Shraddha's parents took her grandfather to the eye specialist as he was complaining of difficulty in seeing things. The doctor diagnosed it as cataract and said that it is quite common in old age. What is cataract? How is it caused? How can it be corrected?
Answer:
Cataract: the eye lens becomes cloudy (milky) so that vision becomes blurred, and there may be partial or complete loss of vision.
Cause: it usually occurs in old age, when the crystalline lens becomes milky and cloudy.
Correction: by cataract surgery, in which the cloudy lens is removed and an artificial lens is inserted. Spectacles cannot correct it.
In simple words: Cataract is a cloudy lens, treated by a simple operation.

Teacher's Note:
1. Cause and cure should both be written.
2. Values: caring for the elderly.

Question 12. Pankaj noticed that while reading books or newspapers, most people keep the book neither too far nor too close to their eyes. So, he tried to find out what happens when he reads the book by keeping it quite far. He found that he could not read all letters clearly. When he tried to read the book by keeping it very close to his eyes, the letters became blurred and his eyes started paining. (A) Explain why Pankaj is not able to read the letters clearly when he keeps the book very close to his eyes. (B) Write the sequence of events that take place when the human eye changes its focus from a distant object to an object closer to the eye.
Answer:
(A) The eye lens cannot become thicker than a certain limit, so its focal length cannot be reduced below a certain minimum. For a book closer than the near point (about 25 cm), the image is not formed on the retina, so the letters look blurred. The ciliary muscles are strained, so the eyes ache.
(B) (1) The ciliary muscles contract. (2) The curvature of the eye lens increases and the lens becomes thicker. (3) The focal length of the lens decreases. (4) The image of the near object is formed on the retina and is seen clearly.
In simple words: Very close objects strain the eye muscles and cannot be focused, so the best reading distance is about 25 cm.

Teacher's Note:
1. Give the sequence as numbered steps.
2. Link the pain with the strain on the ciliary muscles.

Question 13. Mars's atmosphere is composed mainly of carbon dioxide, nitrogen, argon, negligible amounts of oxygen, water vapour and methane. Using the information given and based on your knowledge about how rainbows are formed on Earth, explain why rainbow formation is impossible on Mars.
Answer:
A rainbow forms when sunlight is refracted, dispersed and internally reflected by tiny water droplets suspended in the air.
The atmosphere of Mars contains only negligible water vapour and no rain, so there are no water droplets in the air. Without droplets there is no dispersion and no rainbow can be formed on Mars.
In simple words: No water drops in the air means no rainbow.

Teacher's Note:
1. Droplets are the key requirement.
2. Use the same argument as for the Moon.

Question 14. Read the passage and answer the questions.
A person is suffering from hypermetropia (long-sightedness). It is a defect in which a human eye can see far-off objects clearly but is unable to see nearby objects distinctly. The near point of the person is 1.5 m. Assume that the near point of the normal eye is 25 cm.
(i) What type of lens should be used in his spectacles? (ii) What should be the focal length of the lens he uses? (iii) What will be the power of the lens? (iv) Write one possible cause of this defect.
Answer:
(i) A convex lens.
(ii) u = −25 cm and v = −150 cm. 1/f = 1/v − 1/u = −1/150 + 1/25 = 5/150 = 1/30, so f = +30 cm.
(iii) P = 1/f = 1/0.3 = +3.33 D.
(iv) The eyeball is too short (or the focal length of the eye lens is too long).
In simple words: A +3.33 D convex lens brings the near point back to 25 cm.

Teacher's Note:
1. The virtual image must lie at the defective near point.
2. Keep both u and v negative.