Answer:
Explanation:
Let the thickness of the film is t and the refractive index of the material of film is n.
When light travels through a sheet of thickness t, the optical path traveled is nt.
When the path of one of slit is covered by a sheet of thickness t, the optical path becomes
x = ( n - 1) t
As the one fringe is shift, so the optical path changed by one wavelength.
i.e., x = λ
So, λ = ( n - 1) t

Answer:
conductor
Explanation:
A "conductor" is a material that allows the charges to pass freely from one body to the other. This causes a movement among the electrons and this means that<em> the charge will be passed entirely to the object receiving it.</em> This is also called <em>"conductive material."</em>
Examples of conductors are: <em>copper, aluminum, gold, silver, seawater, etc.</em>
The opposite of conductors are called "insulators." These do not allow the free movement of charges from one object to the other.
Examples of insulators: <em>plastic, rubber, paper, glass, wool, dry air, etc.</em>
It is correct, the action is paddling, where you move the water backwards, and the reaction is the boat moving forwards.