Question

Is there a time delay before thin film interference begins?

Answer 1

So thin film interference is when light is half-reflected half-refracted then the reflected and refracted wave interfere with each other to produce another color.

What I don't understand is that the waves are off-sync; not on top of each other. So why do they interfere? And doesn't interference change only amplitude? Why does it affect the wavelength

Answer 2

waves are off-sync; not on top of each other. So why do they interfere? And doesn't interference change only amplitude? Why does it affect the wavelength $\star \star$