Answer:
option A
Explanation:
Given,
wavelength of light,
refractive index of gasoline, n₁ = 1.40
Refractive index of water, n₂ = 1.33
thickness of the film, t = ?
Condition of constructive interference is given by

For minimum thickness of the film m = 0
From the question we can clearly observe that phase change from gasoline to air
so, n = 1.4


Hence, the correct answer is option A
The direction of its displacement wil be
c.northeast
In fact, the dog walks north for 10 meters and east for another 10 meters. The path of the dog can be represented with two vectors, A pointing north (of magnitude 10 meters) and B pointing east (of magnitude 10 meters). The direction of the resultant vector (due to east) will be given by


and the direction will be north-east.