Myopia is also known as :
- A.Far-sightedness
- B.Near-sightedness
- C.Cataract
- D.Presbyopia
Correct answer
Explanation
The correct answer is B, Near-sightedness. A person with myopia sees nearby objects clearly but finds distant objects blurred, which is why the defect is called near-sightedness or short-sightedness. It happens when the eyeball is too long or the eye lens is too curved, so the image of a distant object forms in front of the retina instead of on it. The defect is corrected with a concave (diverging) lens of suitable power, which spreads the rays slightly so that they meet on the retina. Option A is wrong because far-sightedness is hypermetropia, in which near objects are blurred and a convex lens is used. Option C is wrong because a cataract is the clouding of the eye lens, usually with age, treated by surgery. Option D is wrong because presbyopia is the loss of the eye's power of accommodation in old age. Exam tip: myopia, near-sighted, concave lens; hypermetropia, far-sighted, convex lens.
Practice Questions
View allThe correct order of atomic radius of Li, Na, Be and O is
- A.Na > Li > Be > O
- B.Na > Be > Li > O
- C.Be > Li > Na > O
- D.O > Be > Li > Na
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Two trends of the periodic table decide the order. Going down a group, atomic radius increases because each new period adds an electron shell; so sodium, in period 3, is larger than lithium, in period 2, of the same group 1.
Read the full explanation →Why does the Rough Endoplasmic Reticulum look 'rough' under a microscope ?
- A.Due to the presence of ribosomes on its surface
- B.Due to the absence of ribosomes on its surface
- C.Due to the presence of lysosomes on its surface
- D.Due to the presence of mitochondria on its surface
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The endoplasmic reticulum (ER) is a network of membrane tubes and sacs inside the cell. Part of it is studded on the outside with tiny granules called ribosomes, which give it a dotted, rough look under an electron microscope; this part is the rough ER.
Read the full explanation →An aqueous solution of an acid conducts electricity. This is because
- A.It contains hydrogen ion
- B.It contains water molecules
- C.Electricity passes through it
- D.It generates electricity
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When an acid such as hydrochloric acid dissolves in water, it splits into ions: hydrogen ions (H⁺, which join water molecules as hydronium ions, H₃O⁺) and negative ions such as chloride (Cl⁻).
Read the full explanation →A wire of copper having length l and area of cross-section A is taken and a current I is flown through it. The power dissipated in the wire is P. If we take an aluminium wire having same dimensions and pass the same current through it, the power dissipated will be
- A.P
- B.< P
- C.> P
- D.2P
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The power turned into heat in a wire carrying a current I is P = I²R, and the resistance of a wire is R = ρl/A, where ρ is the resistivity of its material.
Read the full explanation →The mass of one mole of a substance in grams is called its
- A.Kilo-gram mass
- B.Gram-mass
- C.Molar-mass
- D.All the above
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The mass of one mole of any substance, expressed in grams, is by definition its molar mass. One mole contains the Avogadro number of particles, about 6.022 × 10 23, so the molar mass links the mass we can weigh to the number of atoms or molecules present.
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