Practice Test: General Science- 6 | Science & Technology for UPSC CSE PDF Download

Question 51. The layer of the atmosphere which reflec ts the radiowaves back to the earth is called________ 

Answer:  ionosphere

Question 52. Why does radio reception improve slightly during the night? 

Answer:  Sunlight affects radio broadcasts to some extent during the day

Question 53. Television signals cannot be received ordinarily beyond a particular distance due to________ 

Answer:  curvature of the earth

Question 54. Planets are________ 

Answer: non-luminous bodies that do not twinkle

Question 55. A small hole in the window of a closed room forms an inverted image of outside building on the opposite wall of the room. This happens because________ 

Answer: of the rectilinear propagation of light

Question 56. ________part of the sun is visible during total solar eclipse. 

Answer: corona

Question 57. The minimum length of a plane mirror in which a person can see himself full-length should be________

Answer: nearly half his height

Question 58. If you walk towards a plane mirror at a speed of 10 cm/ s, at what speed does your image approach you? 

Answer: 20 cm/s

Question 59. If you stand in a room, where two adjacent walls are covered with plane mirrors, the total number of your images formed will be________ 

Answer:  infinite

Question 60. ________type of mirror can be used to obtain the real image of an object.

Answer: concave mirror

Question 61. A dentist’s mirror is a________ 

Answer: concave mirror

Question 62. The type of mirror used in the head-lamps of cars is the________

Answer: parabolic concave mirror

Question 63. When a pencil is partly immersed in water in a slanting position, the immersed portion appears________ 

Answer: bent towards the water surface

Question 64. The sun remains visible for some time after it actually sets below the horizon. This happens due to________ 

Answer: atmospheric refraction

Question 65. If there were no atmosphere, the length of the day would________ 

Answer: decrease

Question 66. The sun and moon appear elliptical near the horizon due to________

Answer: refraction

Question 67. The twinkling of stars can be partly attributed to________ 

Answer: atmospheric refraction

Question 68. Planets do not twinkle because________ 

Answer: they are nearer to us and therefore minor variations in their intensity are not noticeable.

Question 69. A rainbow is formed by the________of light by water droplets. 

Answer: dispersion and total internal reflection

Question 70. When white light passes through a glass prism, it gets dispersed into colours because________ 

Answer: different colours have different speeds in glass

Question 71. The three primary colours are________ 

Answer: blue, green and red

Question 72. When a person enters a dark room from bright light, he is not able to see clearly for a little while because the________ 

Answer:  iris is unable to dilate the pupil immediately

Question 73. In old age, people have to wear spectacles for reading and writing because________ 

Answer: they lose the power of accommodation

Question 74. The sky appears blue because________ 

Answer: the atmosphere scatters blue colours more than the others

Question 75. In upper space, astronauts________see stars during the day. 

Answer: can

Question 76. The sun appears deep orange-red before it sets because________

Answer: its light has to traverse, a thicker atmosphere, therefore, other colours get scattered and do not reach us

Question 77. Soap bubbles show multiple colours when viewed in white light because of________ 

Answer: the interference of the reflected light

Question 78. The technique of recording and reproducing three-dimensional images of objects is known as________ 

Answer: holography

Question 79. When a wave goes from one place to another, it transports________ 

Answer: energy

Question 80. The pitch (or shrillness) of a sound is determined by its________ 

Answer:  frequency

Question 81. A woman’s voice is shriller than a man’s due to________ 

Answer: higher frequency

Question 82. The loudness of a sou nd wave is determi ned by its________ 

Answer: amplitude

Question 83. Sounds cannot travel through________ 

Answer: vacuum

Question 84. Thunder is heard much after a flash of lightning is seen because________ 

Answer: light travels much faster than sound

Question 85. Mach number is used in connection with the speed of________ 

Answer: aircraft

Question 86. A clearly separate echo of a sound is heard when the minimum distance of the reflecting surface from the source of sound is________ 

Answer: 17 m

Question 87. The walls and ceiling of an auditorium are covered with fibrous material, such as glass fibre, to________

Answer: absorb sound and prevent echoes

Question 88. A police van sounding its siren is moving away from an observer. The pitch (shrillness) of the sound from the siren relative to its normal pitch is________

Answer: lower

Question 89. A device used for measuring the depth of the sea is called________ 

Answer: fathometer

Question 90. If a bar magnet, tied in the middle with a thread, were suspended at the north pole of the earth, it would take________ 

Answer: a nearly vertical position with its north pole pointing downward

Question 91. The crackling sound, heard when dry hair is combed with a hard rubber comb, is due to________ 

Answer: small electric sparks

Question 92. A capacitor (condenser) is used in an electrical circuit to________ 

Answer: store electric charge

Question 93. ‘IC chips’ for computers are usually made of________

Answer: silicon

Question 94. Nichrome wire is used as a heating element in many appliances because________ 

Answer:  it has high resistivity and it resists oxidation in air when red hot

Question 95. The starting current of an electric motor is________the current flowing after the motor reaches its normal running speed. 

Answer:  much greater than

Question 96. Energy conversions in a loudspeaker are________ 

Answer: electrical to mechanical to sound

Question 97. Ener gy conversion s takin g plac e in a microphone are________ 

Answer: sound to mechanical to electrical

Question 98. A transformer is a device for________ 

Answer: stepping up (or down) ac voltage

Question 99. In our houses we get 220 V ac . The value 220 represents________voltage. 

Answer: effective

Question 100. The advantage of ac over dc is that________it can be transmitted over long distances with________loss.

Answer: minimum power