Thin Film Interference Flashcards
If a patient has a cataract, can you assess visual performance of his/her neural system to determine if surgery is justified?
- two coherent points sources placed in a clear part ofhte pupil can be used to stimulate the reinstated with an interference pattern, thus bypassing the the optics to assess the neural system.
- a 100% contrast fringe forms at the retina. This clever technique permits the clinician to test the neural system of the patietns eye without contamination by the cataract
Thin film interference is a ________ by amplitude
Division by amplitude
Thin film interference is due to _______ processes. This is the _________
- multiple reflection
- wave effect
For a thin film, what is long enough to cause interference effects?
Coherence length of ordinary light is long enough
Thin film interference is based on two conditions
- Path difference
2. Phase change
Phase reversal
- Gets inverted with fixed ends
- does not get inverted with a free end
When does 180 degree phase change happen?
When light traveling in lower RI medium reflects off higher RI medium
Principle of optical reversibility
In the absence of any absorption, a light ray that is reflected or refracted will retrace its original path if its direction is reversed
Whatever happens on ________, the opposite happens on ________
- reflection
- transmission
Phase change when going from denser to lighter medium
None
Phase change when going from lighter to denser medium
180 degree phase change
Reflected rays in thin film
2t=mlambda/n
Destructive interference
Minimum reflection
Transmitted rays in thin film
2t=mlambda/n
Constructive interference
Maximum transmission
Important factors to consider before resolving thin film interference problem
- path difference
- phase change
- materials on both sides of the thin film
No _______ on transmission
Phase change
