Table of Contents
What is meant by Photoconduction?
Definition of photoconduction : variation of current in a circuit due to the photoconductivity of some part of it under varying illumination.
What is photoconductivity explain its working and applications?
A photoconductor or Photoconductivity is an electrical & optical phenomenon where a material turns into conductive more electrically because of the electromagnetic radiation absorption like infrared light, ultraviolet light, visible light, or gamma radiation.
What is persistent photoconductivity?
Abstract. Materials with persistent photoconductivity (PPC) experience an increase in conductivity upon exposure to light that persists after the light is turned off. Although researchers have shown that this phenomenon could be exploited for novel memory storage devices, low temperatures (below 180 K) were required.
What is the photoconductive effect?
The alteration of electric conductivity produced by the absorption of varying amounts of radiation composed of photons.
What are photoconductive devices explain any one of them?
Some photodetector applications in which photoresistors are often used include camera light meters, street lights, clock radios, infrared detectors, nanophotonic systems and low-dimensional photo-sensors devices.
What causes photoconductivity?
Photoconductivity is the increase in electrical conductivity produced by shining light on a material. A related effect, called the photovoltaic effect is the inducing of voltages by light.
How do you measure photoconductivity?
Experimental Methodology
- Check the ohm law in the contacts in the dark.
- Measure the residual conductivity (residual or dark current Io)
- Measure the steady state photoconductivity for each wavelength.
- Measure the lamp signal for each wavelength, correct according to the detector response (using a rule of three)
What is the principle of photoconductive cell?
Photoconductive cells function by receiving light energy, which in turn frees electrons from their valence bonds in semiconductor material.
What is photoconductive material?
Photoconductive materials are used in the manufacture of photoelectric devices. Typical photoconductive substances consist of germanium, gallium, selenium, or silicon with impurities, also known as dopants , added. Other common materials include metal oxides and sulfides.
What is negative photoconductivity?
In contrast to positive photoconductivity, negative photoconductivity (NPC) refers to a phenomenon that the conductivity decreases under illumination. It has novel application prospects in the field of optoelectronics, memory, and gas detection, etc.
How a photocurrent is produced?
The photocurrent may occur as a result of the photoelectric, photoemissive, or photovoltaic effect. The photocurrent may be enhanced by internal gain caused by interaction among ions and photons under the influence of applied fields, such as occurs in an avalanche photodiode (APD).
Why is photoconductivity important?
Photoconductivity serves as a tool to understand the internal processes in these materials, and it is also widely used to detect the presence of light and measure its intensity in light-sensitive devices.
What are the characteristics of photoconductive cell?
The illumination characteristics of a typical photoconductive cell are shown from which it is obvious that when the cell is not illuminated its resistance may be more than 1 00 kilo ohms. This resistance is called the dark resistance. When the cell is illuminated, the resistance may fall to a few hundred ohms.
What is photoconductive gain?
The photoconductive gain (G) is defined as the increase in. the number of collected carriers per absorbed photon (with. an energy hν) and can be expressed as. G=collected e. absorbed photons =1I /q.
On what factors does photocurrent depend?
The photocurrent generated depends on the following factors:
- Frequency of the incident light.
- The intensity of incident radiation:
- The potential difference between the electrodes:
- The photocurrent depends on the photo metal used.
Why photoelectric effect is important?
The photoelectric effect is widely studied in the fields of quantum chemistry, condensed matter physics, and solid-state chemistry because it helps draw inferences on the properties of solids and the properties of atoms and molecules.
What are the characteristics of photoelectric effect?
The photoelectric effect has three important characteristics that cannot be explained by classical physics: (1) the absence of a lag time, (2) the independence of the kinetic energy of photoelectrons on the intensity of incident radiation, and (3) the presence of a cut-off frequency.
What is law of photoelectric effect?
(i) There is a definite cut off value of frequency below which electrons cannot be ejected by any substance. (ii) Number of emitted electrons are directly proportional to the intensity of light incident. (iii) Kinetic energy of emitted electrons depends on the frequency of incident light on substance.
Who explain photoelectric effect?
The photoelectric effect was discovered in 1887 by the German physicist Heinrich Rudolf Hertz.
What are Photography Ethics?
When we talk about photography ethics, we are talking about applying concepts like responsibility, power, and dignity to how we we take and share photographs. Everyone will answer ethical questions in their own way, based on their own life experience, personal judgments, and photographic vision.
How do I contact the Photography Ethics Centre?
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Are you prepared to face ethical dilemmas as a photographer?
We present examples and raise questions so that photographers are better prepared to face ethical dilemmas when they occur. Experience of working through difficult ethical considerations gives photographers tangible tools to be more effective in their work.