(a) A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length. (b) We see advertisements for eye donation on television or in newspapers. Write the importance of such advertisements.
(a) A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length. (b) We see advertisements for eye donation on television or in newspapers. Write the importance of such advertisements.
(a) The defect of vision is myopia. The ray diagram shows that the image of a distant object is formed in front of the retina. The two possible causes are (i) excessive curvature of the eye lens, or (ii) elongation of the eyeball. The defect can be corrected by using a concave lens of suitable power. (b) The importance of such advertisements is to create awareness about the need for eye donation and to encourage people to donate their eyes after death. This can help restore vision to people who are blind or have low vision due to corneal blindness.
Marking Scheme
- 1Identify the defect of vision
- 2Draw a ray diagram to illustrate the defect
- 3List two possible causes
- 4Draw a ray diagram to show how the defect may be corrected using a lens of appropriate focal length
Hint
Think about the causes of myopia and how it can be corrected.
Quick Oral Answer
Myopia is a defect of vision where a person cannot see distant objects clearly. It can be caused by excessive curvature of the eye lens or elongation of the eyeball. A concave lens of suitable power can correct this defect by bending the light rays away from the normal, allowing the image to form on the retina. Eye donation is important because it can help restore vision to people who are blind or have low vision due to corneal blindness.
Analysis & Explanation
Myopia is a defect of vision where a person cannot see distant objects clearly. The ray diagram shows that the image of a distant object is formed in front of the retina. This can be caused by excessive curvature of the eye lens or elongation of the eyeball. A concave lens of suitable power can correct this defect by bending the light rays away from the normal, allowing the image to form on the retina.
Common Mistakes
- 1Confusing myopia with hypermetropia
- 2Not drawing the ray diagram correctly
- 3Not listing the possible causes correctly
Interesting Facts
Myopia is a common defect of vision that affects many people worldwide.
Eye donation can help restore vision to people who are blind or have low vision due to corneal blindness.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2013?
This question carries 5 marks in the CBSE Class 10 Science 2013 examination.
Which chapter does this question come from in Science?
This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Defects of Vision" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2013 paper?
This is a Long Answer question from Section A in the CBSE Class 10 Science 2013 paper.