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

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