73. A person is walking away from a plane mirror, his image will
(a) Move away from the mirror
(b) Move towards the mirror
(c) Not move
(d) Disappear
74. A person wants to get his image magnified from a concave mirror of focal length 20 cm. He should stand at a distance
(a) Between 20 cm and 40 cm
(b) Of 20 cm
(c) Of 40 cm
(d) Which is more than 40 cm.
75. In short sightedness,
(a) The light rays converge behind the retina
(b) The light rays converge in front of the retina
(c) Vision is not blurred
(d) Cornea is defective
76. Permanent hardness of water is due to the presence of
(a) Sodium chloride
(b) Calcium sulphate
(c) Calcium bicarbonate
(d) Magnesium bicarbonate
77. Radio reception is generally better in night because
(a) The sun weakens the radio waves during day time
(b) There is less atmospheric noise in the night
(c) The velocity of radio waves increases in dark
(d) The moon helps the propagation of radio waves
78. If a man runs with a speed of 1.5 m/s towards the plane mirror, then his image in the mirror will
(a) Move away from the mirror with a speed of 1.5 m/s
(b) Come nearer to the mirror with a speed of 1.5 m/s
(c) Remain stationary
(d) Move away from the mirror with a speed of 3 m/s
79. Elements commonly present in the artificial fertilizer are nitrogen, phosphorus and
(a) Calcium
(b) Barium
(c) Sodium
(d) Potassium
80.The equivalent resistance of two resistors of 10 ohms and 5 ohms joined in parallel is
(a) 3.3 ohms
(b) 5 ohms
(c) 10 ohms
(d) None of these
81. Identical twins are born when
(a) One sperm fertilises the ovum and the zygote gets divided into two separate cells developing independently
(b) Two sperms fertilise one ovum
(c) Two sperms fertilise two ovums simultaneously
(d) One sperm fertilises two ovums
82. The most important use of zinc in the world is
(a) As a galvanising material
(b) For die casting
(c) For the production of rolled zinc
(d) For brass-making