64. Clear nights are colder than cloudy nights because of?
A.Conduction
B.Condensation
C.Radiation
D.Insolation

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65. Speed of sound is the greatest in :(I) Water
A.water
B.Air
C.Glass
D.Glycerin

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66. A gas thermometer is more sensitive than a liquid thermometer because a gas:
A.is lighter than liquid
B.Expands more than a liquid
C.Is easy to obtain
D.Does not change state easily

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67. Which one of the following is used for sun glasses?
A.Pyrex glass
B.Flint glass
C.Crooks glass
D.Crystal glass

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68. The speed of light with the rise in the temperature of the medium:
A.Increases
B.Decreases
C.Remains unaltered
D.Drops suddenly

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69. Clothes keep us warm in winter because they :
A.Supply heat
B.Do not radiate heat
C.Prevent air from contacting the body
D.Prevent the heat of the body from escaping

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70. In a refrigerator what produces the cooling ?
A.The ice which deposits on the freezer
B.The sudden expansion of a compressed gas
C.The evaporation of a volatile liquid
D.None of these

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