Ans: (d)
447. Red Light is used as a dancer signal because
   (a) it is pleasing to the eye
   (b) it has a traditional colour
   (c) it is easily distinguishable
   (d) it is most sensitive to the human eye
Ans: (d)
448. "Acoustics" is a branch or study dealing with
   (a) historical sites
   (b) architecture
   (c) sound
   (d) trigonometry
Ans: (c)
449. A workman was working on a rail track. A young boy at a distance holds
   his ear close to the railway track. The boy was able to hear the sound of each
   blow or the workman twice. It is because
   (a) speed of sound is greater in steel than in air
   (b) speed of sound is greater in air than in steel
   (c) part of sound waves is reflected between rail tracks
   (d) the boy"s ears are at a different distance from the source
Ans: (a)
450. When a ship floats on water, the weight or water displaced is
   (a) an indeterminate quantity
   (b) equal to the weight of the ship
   (c) greater than the weight of the ship
   (d) less than the weight of the ship
Ans: (b)
451. The speed of light is minimum while passing through
   (a) air
   (b) glass
   (c) vacuum
   (d) water