Interference Flashcards
(31 cards)
With a double slit, when the two waves travel the same distance, is the fringe bright or dark?
Bright!
-also normally in the center
In double slit, if the waves travel a different distance, is the fringe always dark?
Nope
When waves travel different distances, when is the fringe bright?
When the difference is distance is by 1 wavelength
When the waves travel different distances, when is the fringe dark?
When the difference is by a wavelength and a half or some form of a half
what is needed for the proper condition for interference?
- monochromatic light (same color, same wavelength)
- mutual coherence(protons don’t spread)
interference obeys the laws of what?
conservation of energy
which type of interference is for bright fringes and what type is for dark?
bright=constructive
dark=destructive
as the slit distance narrows, the angle gets…
bigger!
-angle increases as slit distance narrows
for a fixed wavelength, what happens the the width of the fringes in regards to d (slit distance)
smaller d=slits closer together=wider fringe
larger d=slits farther apart=narrower fringe
for a fixed slit distance (d), what happens to the width of the fringes in regards to wavelength?
larger wavelength=wider fringes=more spread out
smaller wavelength=narrower fringes=less spread out
what color has a wider fringe, blue or red?
red, they are spread out farther because it has a larger wavelength
white light illumination has what kind of fringes?
colored
if the width of the fringes is reduced, is the angle reduced or greater?
reduced!!!!!!!
-reduced wavelength=reduced angle=reduced space between orders=reduced width of fringe
how can a clinician bypass the the optics (cataract) to look at the neural system?
-use two coherent points in a clear part of the pupil and a 100% contrast fringe forms on the retina as an interference pattern
thin film interference is based on what two conditions?
- path difference
- phase change
when does light undergo a phase change?
-when light traveling in a lower index of refraction medium REFLECTS off a higher index of refraction medium
what is the principle of optical reversibility?
in the absence of absorption, a light ray that is reflected or refracted will retrace its original path if its direction is reversed
what is the rule about reflected and transmitted rays?
-whatever happens on reflection, the opposite happens on transmission
what are the three things you must consider before solving a thin film interference problem?
- path difference
- phase change
- materials on both sides of the thin film
how much of light incident on spectacle lost?
8.4%
what material is close enough to the ideal index of refraction for anti-reflective film (1.234)
magnesium fluoride
what is optical thickness?
the product of of the thickness and refractive index
the minimum thickness of an anti-reflective thin film on glass is_______________
a quarter of the wavelength in the thin film (tn=wavelength/4)
what is the original amount of front surface refelction and what does MgFl reduce it to?
originally is 4.3% and it is reduced to 1.5%
