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
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
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Mass of one oil = \(\frac{5 \times 10^{-4}}{1000}\)
= 5 x 10\(^{-7}\)kg
Density = \(\frac{\text {mass}}{\text{area x thickness}}\)
500 = \(\frac{5 \times 10^{-7}}{\text{0.5 x thickness}}\)
thickness = 2 x 10\(^{-9}\)m
Source: Myschool Past Questions Archive (Record #28863)