# In a laboratory accident, you spill two liquids onto water (separately), neither of which mixes...

## Question:

In a laboratory accident, you spill two liquids onto water (separately), neither of which mixes with the water. They both form thin films on the water surface. As the films spread and become very thin, you notice that one film becomes bright and the other black in reflected light. Why might that be?

## Interference:

It is the phenomena in which the electromagnetic waves of different wavelength are been bombarded to the surface called slit which ultimately makes it unite and results in different pattern types on it. This phenomenon helps it to come down in accurate energy level.

## Answer and Explanation:

This is due to interference with a thin film. In this case on flim is such that it makes constructive interference due to its refractive index and change in the path so appears to be more bright and other makes destructive interference and so appears to be dark.

This can be represented by the mathematical equation as:

For constructive interference: {eq}2nd \times cos \theta = odd \enspace multiple \enspace of \enspace \dfrac{\pi}{2} {/eq}

For destructive interference: {eq}2nd \times cos \theta = integer \enspace multiple \enspace of \enspace \pi {/eq}