# Destructive interference and energy conservation

In case of interference,we know,energy is neither destroyed,nor created; but only redistributed.But in the case of an extremely thin film,due to a reflection and hence a phase difference of pi, the film always appears dark due to destructive interference. So,where does the energy go?

• A phase difference of $\pi$ is required for destructive interference, not $\frac{\pi}{2}$. – Chris Nov 23 '17 at 4:13