641. Radioactivity was first discovered by
A. Pasteur
B. Newton
C. Henry Becquerel
D. None of these
642. Which gas is commonly used in balloons and airships?
A. Hydrogen
B. Helium
C. Carbon
D. None of these
643. A slow-running pendulum clock can be speeded up b
A. Increasing the length of rod
B. Increasing the weight of the bob
C. Reducing the length of the rod
D. None of these
644. A man is standing on a weighing machine in a lift which is moving. The weighing machine will show MINIMUM reading when, the lift is moving
A. Upward with Uniform speed
B. Downward with the Uniform speed
C. In a free fall due to failure of the lift mechanism
D. None of these
645. The approximate intensity level of the sound which can cause damage to the ear drum is
A. 20dB
B 60dB
C. 100dB
D. None of these
646. Deficiency of Vitamin-A results in which of the following problems?
A. Night blindness
B. rickets
C. scurvy
D. hair fall
E. None of these
647. The lifespan of Red Blood Cells is how many days?
A. 150
B. 120
C. 170
D. 240
E. None of these
648. What is the density of water?
A. 1 g/cm3
B. 1.4 g/cm3
C. 2.3 g/cm3
D. none of these
E. None of these
649. Radioactivity was discovered by which of the following scientists?
A. Kelvin
B. Thomson
C. Rutherford
D. Becquerel
E. None of these
650. Severe deficiency of Vitamin D results in which of the following problems?
A. scurvy
B. rickets
C. night blindness
D. osteomalacia
E. None of these