Edited Invalid date
27.7 Thin Film Interference
The intensity in the focal spot increases.
The chance of photodegrading the specimen increases with the higher the.
The spot never becomes a true point.
The bright colors seen in an oil slick floating on water are caused by interference.
The colors that interfere are the bright ones.
When light interacts with something similar to its wavelength, interference effects are most prominent.
A thin film is smaller than the wavelength of light.
The soap bubbles are exposed to sunlight.
The incident light is reflected from the top of the film.
The remainder is reflected from the bottom of the film.
Light reflected from the bottom of the film can interfere with light reflected from the top.
Since the ray that enters the film travels a greater distance, it may be in or out of phase.
Again, consider the bubbles in.
The bubbles are very thin.
If you observe a soap bubble carefully, you will notice that it gets dark at the point where it breaks.
The answer is that a phase change can happen.
Light hitting a thin film is partially reflected and partially reflected at the top surface.
The rays are partially reflected at the bottom and emerge as ray 2.
The rays will interfere in a way that depends on the thickness of the film.
When the film is very thin, the path length difference between the two rays is insignificant, they are out of phase, and the soap bubble will be dark here.
Thin film interference is caused by the thickness of the film relative to the wavelength of light.
A series of cameras.
Light can affect the clarity of the images.
Thin film interference can be caused by a thin layer of magnesium fluoride coating on the lens.
The glass has an index of 1.52.
There will be a shift in the reflection of ray 1 and ray 2.
To get destructive interference, ray 2 needs to travel a half wavelength farther than ray 1.
The path length difference for rays is.
Since light over a broader range of incident angles will be reduced in intensity, films such as the one in this example are most effective in producing destructive interference.
Non-reflective coating is only an approximately correct description since other wavelengths will only be partially cancelled.
Car windows and sunglasses have non-reflective coating.
When the path length difference for the two rays is an integral or half-integral wavelength, thin film interference is most constructive.
If there is a phase change upon reflection, you must determine if interference is constructive or destructive.
Thin film interference depends on a number of factors.
As the thickness of the film changes, you will see rainbow colors of constructive interference for various wavelengths.
The soap's index of refraction is the same as the water's.
Figure 27.33 shows a bubble.
There is a shift for ray 1 reflected from the top surface of the bubble, and no shift for ray 2 reflected from the bottom surface.
The path length difference is an integral multiple of the wavelength.
Since there is a phase change at the top surface, the first occurs for zero thickness.
If the bubble was illuminated with pure red light, we would see bright and dark bands increasing in thickness.
First would be a dark band at 0 thickness, then a bright band at 122 thickness, then a dark band at 244 thickness, then a bright band at 488 thickness, and finally a bright band at 610 thickness.
The bands would be evenly distributed if the bubble varied smoothly in thickness.
The slides are very flat and the wedge of air between them increases in thickness very uniformly.
A phase change occurs at the second surface but not the first, and so there is a dark band where the slides touch.
As the distance between the slides increases, the rainbow colors of constructive interference change from violet to red.
The bands are more difficult to see as the layer of air increases.
If white light is used instead of pure-wavelength light, bright and dark bands can be obtained.
Thin film interference is found in the manufacturing of optical instruments.
Each successive ring of a given color indicates an increase of only one wavelength in the distance between the lens and the blank, so that great precision can be obtained.
There will be no rings once the lens is perfect.
"Newton's rings" interference fringes are produced when two plano-convex lenses are placed together with their plane surfaces in contact.
Thin film interference causes certain butterflies and moths to have iridescent colors.
The wing's color is affected by a number of factors, including constructive interference of certain wavelength reflected from its filmcoated surface.
Special paint jobs that use thin film interference to produce colors that change with angle are offered by car manufacturers.
This expensive option is based on thin film path length differences.
Thin film interference, gratings, or holograms are used in security features on credit cards and similar items that are prone to forgery.
Australia was the first to use dollar bills with a security feature making them difficult to forge.
The United States currency has a thin film interference effect, while other countries such as New Zealand and Taiwan use similar technologies.
Determine if interference is involved by examining the situation.
Slits or thin film interference can be considered in the problem.
Diffraction gratings and double slits produce similar interference patterns, but the gratings have narrower maxima.
There are two maxima to the sides of a single slit pattern.
Take note of the path length difference between the two rays that interfere if thin film interference is involved.
The wavelength in the medium is different from the wavelength in the vacuum.
There is an additional phase shift when light reflects from a medium with a higher index of refraction.
Identifying the unknowns will help determine exactly what needs to be determined in the problem.
A written list can be useful.
You can draw a diagram of the situation.
It's useful to label the diagram.
A list of what can be inferred from the problem can be made.
Enter the knowns and solve the appropriate equation for the quantity to be determined.
View flashcards and assignments made for the note
Getting your flashcards
Privacy & Terms