Geometry in Thin Film Interference Patterns.

During interference in thin flims colours appear due to interference between the light waves reflected from the top and bottom surfaces of the thin film. But the waves reflected or transmitted are parallel to each other. How do they then interfere?
- Nivedhika (age 15)
Namakkal,Tamil nadu,India

Hi Nivedhika,

Glad you are thinking critically about the things you learn!

You have probably seen diagrams (like on wikipedia) in which individual rays are drawn. In reality, beams always have a width, so parts of the beam will usually overlap upon reflection(s). If you drew this using rays, then your diagram would show several incoming rays, and any overlapping rays going out would be from two different rays going in.

Hope that helps.

David Schmid

(published on 06/05/2013)