
In
optics
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...
, a Rayleigh interferometer is a type of
interferometer
Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...
which employs two beams of light from a single source. The two beams are recombined after traversing two
optical paths, and the
interference
Interference is the act of interfering, invading, or poaching. Interference may also refer to:
Communications
* Interference (communication), anything which alters, modifies, or disrupts a message
* Adjacent-channel interference, caused by extra ...
pattern after recombination allows the determination of the difference in path lengths.
Principle of Operation

Light from a source (left) is collimated by a lens and split into two beams using slits. The beams are sent through two different paths and pass through compensating plates. They are brought to a focus by a second lens (bottom) where an
interference pattern
In physics, interference is a phenomenon in which two coherent waves are combined by adding their intensities or displacements with due consideration for their phase difference. The resultant wave may have greater amplitude (constructive int ...
is observed to determine the
optical path
Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium.
The geometrical optical-path length or simply geometrical path length (GPD) is the length of a segment in a given OP, i.e., the Euclidean dis ...
difference in terms of wavelengths of the light.
Advantages and disadvantages
The advantage of the Rayleigh interferometer is its simple construction. Its drawbacks are (i) it requires a point or line source of light for good fringe visibility, and (ii) the fringes must be viewed with high magnification.
See also
*
List of types of interferometers
An interferometry, interferometer is a device for extracting information from the superposition of multiple waves.
Field and linear interferometers
*Air-wedge shearing interferometer
*Astronomical interferometer / Michelson stellar interferomet ...
References
{{Reflist
Interferometers