A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Photo
Conductor
It is an
optoelectronic device that absorbs optical energy and converts into electrical
energy. The operation of device is based on increase of conductivity of a
specific region with photo excitation. The photo generated electrons and holes
are collected by opposite contacts and result in a photo current.
Photo
Detector
An optoelectronic device that absorbs
optical energy and converts it into electrical energy, which usually manifests
as photo current is called as photo detector.
Photo
Diode
It is a reverse
biased PN junction diode which gives current when light falls on it. If the
energy of incident light is greater than forbidden gap energy than the valence
electrons absorb this energy and gas excited to conduction band. In this way
they lead to photo current.
Photo
Fission
Fisssion induced
in some nuclei by absorption of high energetic photons.
Photo
Multiplier Tube
It
is a highly sensitive photo cell, converting light energy into electrical
energy. Scintillations from luminescence material are made to incident on photo
cathode which generates electrons due to electric effect.
Photo
Transistor
A transistor that
regulates current or switches it ‘on’ and ‘off’ based on the intensity of the
light it is exposed to rather than an external electric signal.
Photo
cell
A device in which
the photoelectric or photovoltaic effect or photoconductivity is used to
produce a current or voltage when exposed to light or other electromagnetic
radiation. They are used in exposure meters, burglar alarms, etc.
Photoelectric
Effect
This absorption
process refers to an interaction of the incident photon of energy greater than
binding energy of a bound electron of absorber atom, as a result of which
entire photon energy is absorbed and electron is ejected.
Photoelectron
Terminology
attributed to the electron ejected from a work substance by photoelectric
effect.
Photographic
Film
Photographic film
may be utilized in x-ray work and dosimetry. The film tends to darken when
exposed to radiation. This general darkening of the film is used to determine
overall radiation exposure. Neutron scattering produces individual proton
recoil tracks. Counting the tracks yields the film’s exposure to fast neutrons.
Filters are used to determine the energy and type of radiation. Some typical
filters used are aluminum, copper, cadmium, or lead. These filters provide
varying amounts of shielding for the attenuation of different energies. By
comparing the exposure under the different filters, an approximate spectrum is
determined.
Photoluminescence
Photoluminescence
spectroscopy is a contactless, nondestructive method of probing the electronic
structure of materials. Light is directed onto a sample, where it is absorbed
and imparts excess energy into the material in a process called
photo-excitation. One of the ways this excess energy can be dissipated by the
sample is through the emission of light, or luminescence. In the case of
photo-excitation, this luminescence is called photoluminescence. The intensity
and spectral content of this photoluminescence is a direct measure of various
important material properties.
Photon
Term attributed
to particle nature of light. The concept evolved in quantum theory proposed by
Max Planck. A photon represents one quantum of electromagnetic energy and is
treated as a fundamental particle in the Standard Model of particle physics. It
has rest mass zero.
Photonics
Branch of physics
which deals with technology or application of electromagnetic energy in terms
of its basic unit photon, incorporating Optics, LASER technology, electrical
engineering, information storage and processing.
Photovoltaic
Effect
Photovoltaic mechanism
is the direct conversion of light into electricity at the atomic level. The
principle behind this effect is photoelectric effect. This effect is used in
solar cells.
PHWR
It is type of
nuclear reactor in which pressurized heavy water is used as both coolant and
moderator. Natural Uranium is used as fuel in the reactor core. The heat
transport system consists of two coolant channels. The primary coolant channel
consists of pressurized heavy water under flow. The secondary coolant channel
consists of light water. The heat transfer from primary to secondary channel makes
light water get boiled and the steam generated is used to run turbines for
conversion of mechanical energy into electrical energy.
Physical
Quantity
A physical
quantity is deļ¬ned as quantity that can be used in mathematical equations of science
and technology. It is characterized by its numerical value (magnitude) and
associated unit.
Physical Sputtering
Cathodic sputtering which doesn’t involve chemical reaction between bombarding gas ions and cathode is known as physical sputtering.
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