How does interference take place in thin films?

Thin film interference occurs when light waves reflecting off the top and bottom surfaces of a thin film interfere with one another. This type of interference is the reason that thin films, such as oil or soap bubbles, form colorful patterns.

How can you tell if thin film interference is constructive or destructive?

Thin film interference can be both constructive and destructive. Constructive interference causes the light of a particular wavelength to increase in intensity. (It brightens a particular color like red, green, or blue.) Destructive interference causes the light of a particular frequency to decrease in intensity.

What causes reflection and interference from thin films?

Reflection and Interference from Thin Films ÎNormal-incidence light strikes surface covered by a thin film ‹Some rays reflect from film surface ‹Some rays reflect from substrate surface (distance d further) ÎPath length difference = 2d causes interference ‹From full constructive to full destructive, depending on λ d n 1 n 2 n 0= 1

What causes bright colors on a thin film?

The bright colors seen in an oil slick floating on water or in a sunlit soap bubble are caused by interference. The brightest colors are those that interfere constructively. This interference is between light reflected from different surfaces of a thin film; thus, the effect is known as thin-film interference.

What happens when light strikes a thin film?

Light striking a thin film is partially reflected (ray 1) and partially refracted at the top surface. The refracted ray is partially reflected at the bottom surface and emerges as ray 2. These rays will interfere in a way that depends on the thickness of the film and the indices of refraction of the various media.

Can a phase change occur in a thin film?

For very thin films, the difference in path lengths of rays 1 and 2 in Figure 3.12 is negligible, so why should they interfere destructively and not constructively? The answer is that a phase change can occur upon reflection, as discussed next.