8th Class Science Light Question Bank

done Light Formative Objective Problems Total Questions - 32

• question_answer1)
  Statement I: The plane containing the incident ray and the normal is called plane of incidence. Statement II: The plane containing the incident ray and the normal is called plane of reflection.
  A)
   Both Statements are true, Statement-II is the correct explanation of Statement-I. done clear
  B)
   Both Statements are true. Statement-II is not correct explanation of Statement-I. done clear
  C)
   Statement-I is true, Statement-II is false. done clear
  D)
   Statement-I is false. Statement-II is true. done clear
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• question_answer2)
  When the rays of light, diverging from a point, after reflection or refraction, appear to diverge from another point, then the image so formed is called
  A)
   Virtual image                    done clear
  B)
   Real image done clear
  C)
   Both (a) and (b)               done clear
  D)
   Neither (a) nor (b) done clear
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• question_answer3)
  When the rays of light, diverging from a point, after reflection or refraction actually converge at some other point then that point is ___ image of the object
  A)
   Virtual                  done clear
  B)
   Real done clear
  C)
   Both (a) and (b)               done clear
  D)
   Neither (a) nor (b) done clear
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• question_answer4)
  You are standing in front of a plane mirror, which is approaching you with a speed of 10cm/sec. Then the speed of the image approaching you will be
  A)
   20 cm/s           done clear
  B)
   10 cm/s done clear
  C)
   15 cm/s               done clear
  D)
   25 cm/s done clear
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• question_answer5)
  A lady dressed in a new sari stands in front of a plane mirror fixed on a vertical wall, height of the lady is 160 cm and that of her eyes from the ground is 150 cm, then The length of the mirror required to see her fall view in the mirror is
  A)
   160 cm                 done clear
  B)
   100 cm done clear
  C)
   80 cm             done clear
  D)
   320 cm done clear
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• question_answer6)
  In the above problem, find the position of lower edge of the mirror relative to the ground is
  A)
   160 cm                 done clear
  B)
   75 cm done clear
  C)
   100 cm            done clear
  D)
   200 cm done clear
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• question_answer7)
  A lady dressed in a new sari stands in front of a plane mirror fixed on a vertical wall, height of the lady is 160 cm and that of her eyes from the ground is 150 cm, then find the position of upper edge of the mirror relative to the ground is
  A)
   155 cm          done clear
  B)
   160 cm done clear
  C)
   100 cm                 done clear
  D)
   200 cm done clear
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• question_answer8)
  Statement I: A concave mirror has a real focus. Statement II: A convex mirror has a virtual focus.
  A)
   Both Statements are true. Statement-II is the correct explanation of Statement-I. done clear
  B)
   Both Statements are true. Statement-II is not correct explanation of Statement-I. done clear
  C)
   Statement-I is true. Statement-II is false. done clear
  D)
   Statement-I is false. Statement-II is true. done clear
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• question_answer9)
  The image formed by a convex mirror of real object is larger than the object.
  A)
   When u < 2f      done clear
  B)
   When u > 2f done clear
  C)
   for all values ofu              done clear
  D)
   for no value of u done clear
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• question_answer10)
  Statement I: The radius of curvature and focal length of convex mirror are 80 cm and 40 cm Statement II: The relation between radius of curvature and focal length is R = 2f.
  A)
   Both Statements are true, Statement-II is the correct explanation of Statement-I. done clear
  B)
   Both Statements are true, Statement-II is not correct explanation of Statement-I. done clear
  C)
   Statement-I is true. Statement-II is false. done clear
  D)
   Statement-I is false. Statement-II is true. done clear
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• question_answer11)
  The property that which a light a ray passes obliquely from one medium into another it bends at interface is
  A)
   Reflection         done clear
  B)
   Refraction done clear
  C)
   Interference                     done clear
  D)
   Polarization done clear
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• question_answer12)
  Light starting from a medium of refractive index \[\mu \] undergoes refraction into a medium \[{{\mu }^{\text{l}}}\] If i and r stand for angles of incidence and refraction respectively, then
  A)
   \[\frac{\sin i}{\sin r}=\frac{\mu }{{{\mu }^{\text{l}}}}\]                  done clear
  B)
   \[\frac{\sin i}{\sin r}=\frac{{{\mu }^{\text{l}}}}{\mu }\] done clear
  C)
   \[\frac{\cos i}{\cos r}=\frac{{{\mu }^{\text{l}}}}{\mu }\]                                done clear
  D)
   \[\frac{sini}{sinr}=\frac{1}{\mu {{\mu }^{\text{l}}}}\] done clear
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• question_answer13)
  When a light ray passes from one medium \[({{\mu }_{1}})\] to other medium \[({{\mu }_{2}})\]. Refraction does not take place in the following situation.
  A)
   for normal incidence done clear
  B)
   \[{{\mu }_{1}}>{{\mu }_{2}}\] done clear
  C)
   \[{{\mu }_{1}}={{\mu }_{2}}\]            done clear
  D)
   \[{{\mu }_{1}}<{{\mu }_{2}}\] done clear
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• question_answer14)
  Light of the wave length \[7200{{A}^{o}}\] in air has a wave length in glass is equal to (\[\mu =1.5\])
  A)
   \[7200\overset{\text{o}}{\mathop{\text{A}}}\,\]           done clear
  B)
   \[4800\overset{\text{o}}{\mathop{\text{A}}}\,\] done clear
  C)
   \[1080\overset{\text{o}}{\mathop{\text{A}}}\,\]           done clear
  D)
   \[3600\overset{\text{o}}{\mathop{\text{A}}}\,\] done clear
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• question_answer15)
  A ray of light incident on a refracting surface. If the angle of incidence \[{{60}^{o}}\] and the angle of refraction is \[{{45}^{o}}\], then angle of deviation is
  A)
   \[{{30}^{o}}\]                                    done clear
  B)
   \[{{90}^{o}}\]     done clear
  C)
   \[{{15}^{o}}\]                    done clear
  D)
   \[{{0}^{o}}\] done clear
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• question_answer16)
  The velocity of light in air is \[3\times {{10}^{8}}m{{s}^{-1}}\] and in glass is \[2\times 108m{{s}^{-1}}\].. The refractive index of glass w.r.t air is
  A)
   2/3        done clear
  B)
   3/2    done clear
  C)
   4/3                        done clear
  D)
   9/4 done clear
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• question_answer17)
  A fish is raising vertically to the surface of water in a lake uniformly at the rate of \[2m{{s}^{-1}}\] observes a bird diving vertically towards the water at a rate \[4m{{s}^{-1}}\] vertically above it. The refractive index of water is 4/3. The actual velocity of the bird is
  A)
   3/2        done clear
  B)
   2/3     done clear
  C)
   4/3                        done clear
  D)
   3/4 done clear
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• question_answer18)
                  Which of the following diagrams correctly represents the ray of light passing through the optical centre?
  A)
    done clear
  B)
                done clear
  C)
                done clear
  D)
    done clear
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• question_answer19)
  A ray of light is incident on a concave lens parallel to its principal axis. The path of the refracted ray is correctly depicted by
  A)
    done clear
  B)
    done clear
  C)
    done clear
  D)
     done clear
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• question_answer20)
  An object AB is placed in front of a convex lens at its principal focus as shown in the Figure. Which of the ray diagram given below correctly depicts the refraction through the lens L?
  A)
    done clear
  B)
    done clear
  C)
    done clear
  D)
     done clear
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• question_answer21)
  Which of the following parts of the eye has enormous number of photo-sensitive cells?
  A)
   Iris                                         done clear
  B)
   Pupil done clear
  C)
   Retina              done clear
  D)
   Cornea done clear
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• question_answer22)
  The focal length of the eye lens is adjusted by the
  A)
   vitreous humour             done clear
  B)
   aqueous humour done clear
  C)
   ciliary muscles     done clear
  D)
   optic nerves done clear
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• question_answer23)
  In the human eye, the function of the optic nerves is to
  A)
   adjust the focus of the eye lens done clear
  B)
   transmit electrical signals to the brain done clear
  C)
   control the number of rod and cone cells done clear
  D)
   convert light signals into electrical signals done clear
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• question_answer24)
  The primary function of the crystalline lens in the human eye is to
  A)
   reduce the intensity of light done clear
  B)
   focus the incident light rays done clear
  C)
   adjust the size of the pupil done clear
  D)
   filter out the dust particles done clear
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• question_answer25)
  The given diagram is that of the human eye. In the given diagram, the parts labelled as I and II are respectively the
  A)
   eye lens and the cornea done clear
  B)
   pupil and the eye lens done clear
  C)
   cornea and the pupil done clear
  D)
   pupil and the iris done clear
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• question_answer26)
  Four statements about the blind spot of the human eye: I It is devoid of photosensitive cells. II No image is formed at the blind spot. III It connects the optic nerves to the retina. IV Its malfunctioning makes a person blind. Which of the given statements is incorrect?
  A)
   I                                              done clear
  B)
   II done clear
  C)
   III                           done clear
  D)
   IV done clear
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• question_answer27)
  When we look at a distant object, the ciliary muscles__i__, making the eye lens __ii__. This iii the focal length of the eye lens so that the image of that object gets focused on the retina. The information in which alternative completes the given statements?
  A)
   i-get released, ii-thicker, iii-decreases done clear
  B)
   i-contract, ii-thicker, iii-increases done clear
  C)
   i-get released, ii-thinner, iii-increses done clear
  D)
   i-contract, ii-thinner, iii-decreases done clear
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• question_answer28)
  Which of the following pairs of eye parts is responsible for controlling the amount of light entering into the eye?
  A)
   Iris and pupil done clear
  B)
   Cornea and eye lens done clear
  C)
   Cilliary muscles and iris done clear
  D)
   Cilliary muscles and pupil done clear
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• question_answer29)
  Tina has a defect in her eyes. She is not able to contract her iris properly. As a result of the defect in her eyes, Tina will not be able to see
  A)
   in dim light         done clear
  B)
   near objects done clear
  C)
   in bright light     done clear
  D)
   distant objects done clear
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• question_answer30)
  The range of vision of a normal human eye lies between
  A)
   25 m and infinity              done clear
  B)
   2.5 m and 5 km done clear
  C)
   2.5 cm and 5 km               done clear
  D)
   25 cm and infinity done clear
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• question_answer31)
  Myopia is a defect of vision caused by
  A)
   a decrease in the retinal distance from the lens done clear
  B)
   a decrease in the diameter of the eyeball done clear
  C)
   an increase in the thickness of the lens done clear
  D)
   an increase in the curvature of the lens done clear
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• question_answer32)
  Shyam views a certain object and finds that it is not properly visible to him. The image of the said object is formed by his eye lens 3 cm away from the pupil of his eye.Shyam can correct the defect in his vision by using
  A)
   convex lens    done clear
  B)
   bifocal lens done clear
  C)
   concave lens    done clear
  D)
   cylindrical lens done clear
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