Myopia, or short-sightedness, is corrected by using which type of lens?
- A.Convex lens
- B.Concave lens
- C.Cylindrical lens
- D.Bifocal lens
Correct answer
Explanation
The correct answer is B, a concave lens. In myopia the eyeball is too long or the lens too strongly curved, so light from a distant object is brought to a focus in front of the retina and the distant object appears blurred. A concave lens diverges the rays before they enter the eye, pushing the focus back on to the retina. Option A is wrong because a convex lens is used for hypermetropia, or long-sightedness, where the image is formed behind the retina and the rays need to be converged a little earlier. Option C is wrong because a cylindrical lens is used for astigmatism, which is caused by an uneven curvature of the cornea. Option D is wrong because a bifocal lens is used for presbyopia, the loss of the power of accommodation in old age, where a person needs one correction for distance and another for reading.
Read the full article: Sense Organs: Eye, Ear, Nose, Tongue and Skin
Practice Questions
View allWhich part of eye controls size of a pupil?
- A.Cornea
- B.Iris
- C.Retina
- D.Eye Lens
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The iris is the coloured ring in front of the lens, formed by the front part of the choroid, and the muscles in it widen or narrow the pupil so that the right amount of light reaches the retina; in dim light the pupil opens wide and in bright light…
Read the full explanation →Which of the following parts of the human body contains gustatory receptors?
- A.Eyes
- B.Nose
- C.Tongue
- D.Skin
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Gustatory receptors are the receptors of taste, and they lie in the taste buds of the tongue, which sit mostly on small projections called papillae; they are stimulated by chemicals dissolved in saliva and send impulses to the brain.
Read the full explanation →Which is the smallest bone in the human body?
- A.Malleus
- B.Incus
- C.Stapes
- D.Nasal bone
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The stapes, also called the stirrup because of its shape, lies in the middle ear and is the smallest bone in the human body; it passes the vibration received from the eardrum on to the oval window of the inner ear.
Read the full explanation →Which part of the ear is responsible for maintaining the balance of the body?
- A.Cochlea
- B.Semicircular canals
- C.Tympanic membrane
- D.Eustachian tube
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The three semicircular canals of the inner ear are set at right angles to one another and are filled with fluid; movement of the head moves the fluid, which stimulates the receptors and tells the brain about the position and motion of the head, so that balance or equilibrium is…
Read the full explanation →The light sensitive layer of the human eye on which the image is formed is the:
- A.Cornea
- B.Choroid
- C.Sclera
- D.Retina
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The retina is the innermost coat of the eyeball and it carries the photoreceptor cells, the rods and the cones, which convert light into nerve impulses that the optic nerve carries to the brain; the image formed on the retina is real and inverted, and the brain interprets it as…
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