The mirrors used as rear-view mirrors in vehicles are
- A.concave
- B.convex
- C.cylindrical
- D.plane
Correct answer
Explanation
The correct answer is B, convex. A convex mirror always forms an erect, diminished image, so it shows a much wider area of the road behind than a flat mirror of the same size, which is why it is used as a rear-view or side-view mirror. A convex mirror bulges outward and its focus lies behind the mirror. Whatever the position of the object, the image is virtual, upright and smaller, which packs a wide field of view into a small glass. That is why such mirrors are also put at sharp road bends and in shops for security. The trade-off is that vehicles look farther away than they really are. Option A is wrong because a concave mirror is used for magnification and focusing, as in shaving mirrors, dentists' mirrors and torch reflectors. Option C is wrong because cylindrical mirrors distort images in one direction and are not used for rear view. Option D is wrong because a plane mirror gives a same-size image with a narrow field of view, so it shows too little of the road. Exam tip: convex = rear-view, wide view; concave = shaving mirror, headlights, solar cookers.
Practice Questions
View allWho among the following built a model steam engine in 1698 called "Miner's Friend" to drain mines ?
- A.Thomas Savery
- B.Thomas Newcomen
- C.James Watt
- D.Richard Arkwright
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The English engineer Thomas Savery patented a steam pump in 1698 and called it the Miner's Friend, as it was meant to pump water out of flooded mines.
Read the full explanation →A metallic wire having resistance of 20 Ω is cut into two equal parts in length. These parts are then connected in parallel. The resistance of this parallel combination is equal to
- A.20 Ω
- B.10 Ω
- C.5 Ω
- D.15 Ω
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Each half of the wire has a resistance of 10 Ω, and two 10 Ω resistors in parallel give 5 Ω. The resistance of a wire is R = ρL/A, so it is directly proportional to its length when the material and thickness stay the same.
Read the full explanation →Myopia is a defect in human vision where an image of a
- A.nearby object is focused beyond the retina.
- B.nearby object is focused before the retina.
- C.distant object is focused before the retina.
- D.distant object is focused beyond the retina.
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In myopia, or short-sightedness, a person sees near objects clearly but distant objects look blurred because their image forms in front of the retina.
Read the full explanation →A homogeneous mixture contains two liquids. How are they separated ?
- A.By filtration
- B.By evaporation
- C.By distillation
- D.By condensation
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Two miscible liquids that form a homogeneous mixture are separated by distillation, which uses the difference in their boiling points.
Read the full explanation →Cartilage is NOT found in
- A.larynx
- B.nose
- C.ear
- D.urinary bladder
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The urinary bladder is a hollow muscular sac made of smooth muscle and a stretchable lining; it has no cartilage.
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