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1,000 identical drops of oil of density 500kgm-3 have a total mass of 5 x 10-4kg. One ...

1,000 identical drops of oil of density 500kgm-3 have a total mass of 5 x 10-4kg. One of the drops forms a thin film of area 0.5m2 on water. The thickness of the film is
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  • A 2 x 10-8m
  • B 2 x 10-9m
  • C 2 x 10-7m
  • D 3 x 10-9m
  • E 2.8 x 10-8m
Correct Answer: Option B
Explanation:
Mass of one oil = \(\frac{5 \times 10^{-4}}{1000}\)
= 5 x 10-4kg
Density = \(\frac{\text {mass}}{\text{area x thickness}}\)
500 = \(\frac{5 \times 10^{-7}}{\text{0.5 x thickness}}\)
thickness = 2 x 10-9m

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