Defects of Vision
Physics ⇒ Light and Optics
Defects of Vision starts at 9 and continues till grade 12.
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See sample questions for grade 10
A person can see nearby objects clearly but distant objects appear blurred. Which defect of vision does the person have?
A person has both myopia and hypermetropia. Which type of lens is used to correct this condition?
A person’s far point is 2 m. What is the power of the lens required to correct his vision? (Give your answer in diopters to one decimal place.)
A person’s near point is 100 cm. What is the focal length of the lens required to correct his vision so that he can see clearly at 25 cm? (Give your answer in cm, rounded to one decimal place.)
A person’s near point is 50 cm instead of 25 cm. What type of lens is required to correct this defect?
A student reads a book at 40 cm from his eyes, but the letters appear blurred. His optician prescribes a lens of power +2.5 D. What type of defect does he have?
Describe how a cylindrical lens corrects astigmatism.
Explain the main cause of presbyopia and how it differs from hypermetropia.
Explain why a person with hypermetropia cannot see nearby objects clearly.
Explain why a person with presbyopia may need bifocal lenses.
If the power of a lens required to correct a myopic eye is -2 D, what is the focal length of the lens in meters?
State one difference between myopia and hypermetropia in terms of image formation.
A person is unable to read a book at 25 cm but can see distant objects clearly. Which type of lens should be prescribed to correct this defect, and why?
A person with hypermetropia has a near point at 75 cm. Calculate the power of the lens (in diopters) required to correct his vision so that he can see objects clearly at 25 cm. (Give your answer to one decimal place.)
A person’s far point is 50 cm. What is the nature and focal length of the lens required to correct his vision?
A student is diagnosed with astigmatism. Explain how the shape of the cornea or lens causes this defect and how it affects vision.
Explain why a person with myopia cannot see distant objects clearly, but can see nearby objects without difficulty. Include the role of image formation in your answer.
Explain why bifocal lenses are used to correct presbyopia and describe how they function.
A myopic person uses a lens of power -3.0 D to correct his vision. Calculate the far point of his eye in centimeters.
A person with a near point of 80 cm wishes to read a book at 25 cm. What is the minimum power of the lens (in diopters) required to correct his vision? (Give your answer to one decimal place.)
