Question

A thin layer of colourless oil on water surface looks to be coloured in the sun light, why?

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Answer 1

$\blue{\textbf{Answer}}$:-

➮The thin layer of oil looks to be coloured due to❝ $\blue{\texttt{Interference}}$❞. When sun light falls on the layer of oil, it is reflected from both the upper layer and lower layer of surface.

➮The path difference between the two reflected rays is given by ,

$\blue{\texttt{P}}$ ➭ 2μt cosθ

➮where,

u=$\blue{\texttt{refractive index of layer}}$

t=$\blue{\texttt{thickness of layer}}$

θ = $\blue{\texttt{angle of refraction}}$

If , p ➭n (λ/ 2)

➮Where,

$\textbf{n}$➭ ➋,➍ ,➏ , ...

then layer will appear dark .

and ,if $\textbf{n}$➭ ➊,❸, ❺,➐ , ..

the layer will appear bright.

❝The colours present in the reflected light will depend on the $\blue{\texttt{thickness of the layer}}$.❞

Answer 2

Answer:

The oil layer on the surface of water appears coloured, due to interference