Human Eye And Colourful World Very Short Answer Questions
Question 1. A person with a myopic eye cannot distinctly see objects beyond 1.2 m. What should be the type of corrective lens used to restore proper vision?
Answer: Diverging or concave lens.
Question 2. What are the far and near points of the human eye with normal vision?
Answer: For a human eye with normal vision, the far point is at infinity and the near is at 25 cm from the eye.
Question 3. A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
Answer: The child is suffering from myopia. He should use concave lenses of suitable focal length.
Question 4. What is astigmatism?
Answer: It is a defect in which a person cannot see in all directions equally well.
Question 5. Where does the greatest degree of refraction oflight occur in the eye?
Answer: At the cornea.
Question 6. A man wearingglassesatfocal length of +1 cannot see objects beyond 1 what is the defect in his eye?
Answer: Myopia.
Read and Learn More CBSE Class 10 Science Very Short Answer Questions
Question 7. What is the function of the choroid?
Answer: It, contains black pigments which avoid internal reflections within the eye.
Question 8. What happens to the lens and the ciliary muscles when you are looking at
Answer: The ciliary muscles contract and the lens becomes thick, i.e. its radius of curvature decreases.
Question 9. Define dispersion of white light.
Answer: The splitting of white light into seven colours on passing through a transparent medium, i.e. glass prism, is called dispersion of light.
Question 10. What is presbyopia?
Answer: It is a defect of vision due to which an old person cannot see nearby objects clearly due to loss of power of accommodation of the eye.
Question 11. Name a natural phenomenon which is caused by the dispersion of sunlight in the sky.
Answer: Formation of the rainbow.
Question 12. Give one cause of sightedness.
Answer: Increase the focal length of the eye lens.
Question 13. What would have been the colour ofthe earth’s sky if there were no atmosphere?
Answer: It would have been dark.
Question 14. State one function ofthe crystalline lens in the human eye.
Answer: It produces a real and inverted image of the object on the retina.
Question 15. Name the type of particles which act as a prism in the formation of the rainbow in the sky.
Answer: Water droplets are present in the atmosphere.
Question 16. Name two types of cells in the retina of the eye which respond to light.
Answer: Rods and cones.
Question 17. What is the Tyndall effect?
Answer: The scattering oflight by particles in its path is called the Tyndall effect.
Question 18. On what factor does the colour ofthe scattered light depend?
Answer: It depends on the size of the scattering particles.
Question 19. How is the sense of vision carried from the eye to the brain?
Answer: Through the optic nerve.
Question 20. What is an iris?
Answer: The coloured diaphragm between the cornea and lens.
Question 21. Why does the sky appear dark to astronauts?
Answer: For scattering oflight, particles are required since there are no particles in space the sky appears dark to an astronaut.
Question 22. Give one example of a phenomenon where the Tyndall effect can be observed.
Answer: When a beam of sunlight enters a dusty room through a window, its path becomes visible to us.
Question 23. Give an example of an optical phenomenon which occurs in nature due to atmospheric refraction.
Answer: Advanced sunrise and delayed sunset.
Question 24. A person suffering from an eye defect uses lenses of power -10. Name the defect he is suffering from and the nature of the lens used.
Answer: Myopia, concave lens.
Question 25. Name the condition resulting due to the eye lens becoming cloudy.
Answer: Cataract.
Question 26. Name the two phenomena involved in the formation of a rainbow.
Answer: 1. Dispersion
Question 27. A person is advised to wear spectacles with concave lenses. What types of defect of the vision is he suffering from?
Answer: Myopia or short-sightedness.
Question 28. What is a blind spot?
Answer: A point at which the optic nerve leaves the eye.
Question 29. Why is blind spot so-called?
Answer: An image formed at this point is not sent to the brain.
Question 30. What is the role of the pupil in the human eye?
Answer: The pupil regulates and controls the amount oflight entering the eye.
Question 31. Which colour of white light suffers the least deviation and maximum deviation when a beam of white light passes through a glass prism?
- Red
- Violet
Answer: 2. Total internal reflection
Question 32. What is the range of vision for a normal human eye?
Answer: It is 25 cm to infinity.
Question 33. Name the part of the human eye that helps in changing the focal length of the eye lens.
Answer: Ciliary muscles.
Question 34. Does a beam of white light give a spectrum on passing through a hollow prism?
Answer: No, because dispersion oflight cannot occur through a hollow prism containing prism.
Question 35. Can an observer see a rainbow on the moon1?
Answer: No, there is no atmosphere on the moon.
Question 36. Is the position of a star as seen by us in its true position? Justify your answer.
Answer: No, light from stars undergoes atmospheric refraction which occurs in the medium of gradually changing refractive index.
Question 37. Is the position of a star as seen by us its true position? Justify your answer.
Answer: No. Light from stars undergoes atmospheric refraction which occurs in the medium of gradually changing refractive index.
Question 38. How are we able to see nearby and also the distant objects?
Answer: By use of bifocal length. It enables us to see both distant and nearby objects.
Question 39. Explain why the planets do not twinkle.
Answer: Planets being of larger size can be taken as a collection of large numbers of sized objects/sources oflight, which nullify the twinkling effect of each other.
Question 40. We see advertisements for eye donations on television or in newspapers. Write the importance of such advertisements.
Answer: Such advertisements motivate people to pledge their eyes for donation after death. They also spread awareness about eye donation amongst the people. They dispel myths and misconceptions associated with eye donation.
Question 41. No rainbow could be observed from the surface of the moon by the astronaut. Give reason.
Answer: The moon does not have any atmosphere and no water droplets are present. Hence, no dispersion oflight is possible. Therefore, astronauts cannot see a rainbow from the moon.
Question 42. What are rods and cones?
Answer: These are light-sensitive cells present in the retina. Rods control the intensity of light, while cones control the colour perceptions.