51.

Optical fibre works on the
A. principle of refraction B. total internal reflection
C. scattering D. interference
Answer and Explanation
Answer:B
Explanation: No answer description available for this question.
52.

Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in
A. 4.2 seconds B. 42 seconds
C. 4.2 years D. 42 years
Answer and Explanation
Answer:C
Explanation: No answer description available for this question.
53.

Supersonic plane fly with the speed
A. less than the speed of sound B. of sound
C. greater than the speed of sound D. of light
Answer and Explanation
Answer:C
Explanation: No answer description available for this question.
54.

Mach number is used in connection with the speed of
A. sound B. aircraft
C. spacecraft D. ships
Answer and Explanation
Answer:B
Explanation: No answer description available for this question.
55.

On a stationary sail boat, air is blown from a fan attached to the boat. The boat
A. moves in opposite direction in which the air is blown B. does not move
C. moves in the same direction in which air blows D. spins around
Answer and Explanation
Answer:B
Explanation: No answer description available for this question.