76 .The length of the pendulum isdoubled and the mass of its bob is halved.Its time sperod would
A.  become double
B.  become half
C.  become $\sqrt2 $ times
D.  remain the same
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77 .Vibration magnetometer works on the principle of
A.  torque acting on the bar magnet
B.  force acting on the bar magnet
C.  both the force and the torque acting on the bar magnet
D.  none of these
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78 .Which one of the following is the most stable ecosystem?
A.  Mountain
B.  Ocean
C.  Forest
D.  Desert
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79 .The primary colours in phothgraphy are
A.  red, blue, yellow
B.  red, yellow, green
C.  red, blue, green
D.  red, green, cyan
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80 .Cosmic rays
A.  are charged particles
B.  are uncharged particles
C.  can be charged as well as unchanged
D.  None of the above
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81 .Myopia is due to
A.  shortening of eye ball
B.  irregular changes in the focal length of the eye lens
C.  older age
D.  elongation of eye ball
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82 .A motor converts
A.  mechanical energy into electrical energy
B.  mechanical energy into sound energy
C.  electrical energy into mechanical energy
D.  None of these
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83 .Which of the following is not caused by atmospheric refraction of light?
A.  Sun appearing higher in the sky than it actually is
B.  Sun becoming visible two or three minutes before actual sunrise
C.  Sun appearing red at sunset
D.  Twinkling of stars at night
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84 .What is the difference between aCFL and an LED LAMP?
( 1 ) Toproduce light, a CFL uses mercuryvapour and phosphor while an LED lampuses semi- conductor material.
( 2 ) The average life span of a CFL ismuch longer than of and LED lamp.
( 3 ) A CFL is LESS energy -efficient ascompared to an LED lamp.
Which of the statements given aboveis/are correct?

A.  1 only
B.  2 and 3
C.  1 and 3
D.  1, 2 and 3
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85 .The mercury and sodium street lamps light up because of.
A.  Electron absorption
B.  Electron emission
C.  Atomic emission
D.  Atomic absorption
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86 .The least penetrating power ray is
A.  Ray
B.  X – Ray
C.  γ Ray
D.  Ray
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87 .Different objects at different distances are seen by the eye. The paramenter athe remains. Constent is
A.  the focal length of the eye lens
B.  the object distance from the eye lens
C.  the radii of curvature of the eye lens
D.  the image distance from the eye lens
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88 .Colours of thin films are due to
A.  dispersion of light
B.  interference of light
C.  absorption of light
D.  scattering of light
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89 .The clouds float in the atmosphere because of their low The clouds float in the atmosphere because of their low
A.  1
B. 
C. 
D. 
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90 .X- rays were discovered by-
A.  Roentgen
B.  Becquere
C.  Curie
D.  Van lane
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