121. Microphone is a device in which:
       (a) sound waves are directly transmitted
       (b) electrical energy is converted into sound waves directly
       (c) sound waves are converted into electrical energy and then reconverted into sound after transmission
       (d) amplification is not required at all
Ans : (c)
122. The approximate velocity of light per second is: [UDC 1995]
       (a) 3 x106 m
       (b) 3 x108 m
       (c) 3 x1010 m
       (d) 3 x1012 m
Ans : (b)
123. If one wants to throw a cricket ball to the maximum distance, then he should throw it at an angle of:
       (a) 22 1/2°
       (b) 30°
       (c) 45°
       (d) 60°
Ans : (c)
124. Air-pockets that cause aircrafts to lose altitude suddenly are caused by: [IFS 1990]
       (a) dense cloud cover
       (b) poor visibility
       (c) temperature inversions
       (d) intense low pressure in valleys that suck in air
Ans : (c)
125. Which of the following natural directions of energy transformation are correct? [IFS 1993]
            1) Heat energy to mechanical energy.
            2) Mechanical energy to heat energy.
            3) Heat energy to electrical energy.
            4) Electrical energy to heat energy.
       (a) 1 and 2
       (b) 1 and 3
       (c) 1 and 4
       (d) 2 and 4
Ans : (d)
126. Which of the following statements regarding the uses of diamond are correct ?
            1) Diamond being the hardest substance, is used in glass cutters and rock drilling equipment.
            2) Because of its extraordinary sensitivity to heat rays, diamond is used for making high precision thermometers.
            3) Sharp-edged diamonds are used by eye-surgeons as a tool to remove cataract from eyes.
            4) Because of its ability to keep out the harmful radiations, diamond is used for making protective windows for space
       (a) 1, 2 and 3
       (b) 2, 3 and 4
       (c) 1, 2 and 4
       (d) 1, 2, 3 and 4
Ans : (d)
127. The blue colour of the water in the sea is due to: [Railways 1994]