When the plastic thin film of refractive index `1.45`is placed in the path of one of the interfering waves then the central fringe is displaced through width of five fringes.The thickness of the film will be ,if the wavelength of light is`5890Å`

Explanation

To find the thickness of the plastic thin film that causes the displacement of the central fringe through a width of five fringes, we will follow these steps:

### Step 1: Understand the relationship between fringe displacement and thickness
When a thin film is placed in the path of one of the interfering waves, the displacement of the central fringe (x₀) can be expressed as:
\[ x₀ = (n - 1) \cdot \frac{t \cdot \lambda}{2d} \]
where:
- \( n \) is the refractive index of the film,
- \( t \) is the thickness of the film,
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