TABLE OF CONTENTS:
PHOTONS:
The electromagnetic wave itself is composed of tiny quantum packet of energy called photons.
Measure of energy which an atom can get from an electromagnetic wave-its photon-relying just upon that wavelength.
More limited (shorter) the wavelength, the more energetic the photon. Photons of X-rays and Gamma rays are more energetic due to their shorter wavelengths.
More hotter areas of the Sun, were individual particles have more energy will emanate electromagnetic radiations of shorter wavelength.
PHOTON PR0PERTIES:
Discrete bundle of electromagnetic energy.
Travel at the vacuum speed of light.
Have zero mass and rest energy
Carry energy and momentum.
Electrically neutral.
PHOTOELECTRIC EFFECT:
The peculiarity by which electrons are emitted from certain metal surface, when sufficiently high frequency electromagnetic radiations are allowed to incident on it.
Whenever a unit of light called a photon hits the material it can create a photoelectron in the material which can be distinguished as an electric current flow.
The photoelectric effect occurs with photons having energies from a few electronvolt to over 1 MeV.
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-5627546507063427 (adsbygoogle = window.adsbygoogle || []).push({});The photoelectric effect phenomena (convert light into electricity) used to adjust the automatic iris in various types of cameras, and;in solar cells.
The photoelectric effect is also widely used to investigate electron energy levels in matter.
LAWS OF PHOTOELECTRIC EMISSION:
EXPLANATION OF KINETIC ENERGY:
Experiments showed that kinetic energy of the ejected electrons depends on the frequency of incident light above a threshold value.
Maximum kinetic energy of the emitted electron is linearly proportional to the frequency of the incident radiations above a threshold value.
EXPLANATION OF THE EFFECT OF INTENSITY:
The intensity of the impinging light determines the amount of current generated.
The photoelectric current Is proportional to the light intensity, independent of the frequency of Incident radiation above threshold value.
EXPLANATION OF THRESHOLD FREQUENCY:
Under a specific frequency, the photoelectric impact doesn’t happen by any stretch of the imagination.
The threshold frequency is different for various materials.
CLARIFICATION OF TIME LAG:
The time between the incidence and the outflow of the photoelectron is very small, less than 10-9 second.
WAVE-PARTICLE DUALITY:
Investigation of photoelectric effect is significant in getting the quantum nature of light and the idea of wave-particle duality.
De-Broglie, proposed that light has a double nature. It can act as particles as well waves. Davisson and Germer, given the proof of confirmation of de-Broglie hypothesis of matter waves.
https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-5627546507063427 (adsbygoogle = window.adsbygoogle || []).push({});Waves related with material particles moving are called matter waves. Matter waves are referred as de-Broglie waves. All matter displays wave like way of behaving. Particles like electrons, protons, neutrons and so forth display wave nature when moving.
PARTICLE LIKE PROPERTIES OF LIGHT:
The particle like properties of light is
Photoelectric effect and
Compton effect.
The Phenomena like photoelectric effect and Compton effect etc. can be explained only in terms of quantum theory of light. (By assuming particle nature of light).
PHOTOELECTRIC EFFECT:
The peculiarity by which electrons are emitted from certain metal surface, when sufficiently high frequency electromagnetic radiations are allowed to incident on it.
COMPTON EFFECT:
Compton observed that some parts of X-ray were scattered away from the beam direction with longer wavelength than the incoming radiation in terms of a collision between two particles, one being a free electron and the other the photon.
WAVE LIKE PROPERTIES OF LIGHT:
The wave like properties of light are the phenomena like interference, diffraction, polarisation and dispersion.
SOLAR CELL:
Sun powered cells (solar cells) or Photovoltaic cells are the immediate change of light into electricity at the atomic level. Sunlight based cell is made of silicon (a semiconductor) which is utilized in microelectronic industry.
Solar cell is a junction diode wherein a flimsy silicon wafer is uncommonly treated to shape an electric field (positive on one side and negative on the opposite side).
Just light photons whose energy is equivalent or greater than the band gap of the cell material can free an electron. Current created by a photovoltaic cell straightforwardly subject to how much light strikes the module.
At the point when light energy strikes the sun powered cell, the electrons are taken away from the atoms. This sun powered cell depends on photoelectric effect which are the immediate transformation of light into electricity.
PHOTOVOLAIC MODULES:
During the energy emergency, the photoelectric modules earned the respect. Photovoltaic module is a frame wherein various sun-based cells (solar cells) are electrically connected with one another.
These modules are intended to supply electricity. Current created by a photovoltaic cell straightforwardly reliant upon how much light strikes the module.
ARRAY:
Different photovoltaic modules can be wired together to from an array.
DAVISSON AND GERMER EXPERIMENT:
Davisson and Germer terminated fine collimated beam of electrons at the face a of crystalline nickel target.The angular dependence of the reflected electron intensity as estimated to have a similar diffraction pattern as those anticipated by Bragg for X- ray beams.
The accelerated voltage is shifted, and it was observed that there is areas of strength for a comparing to a sharp diffraction maximum at a speeding up (accelerating) voltage of 54 V.
De Broglie, proposed that light has a double nature. It can act as particles as well as waves .Davisson and Germer, given the verification of affirmation of de Broglie speculation of matter waves.Davisson-Germer analyze affirmed the de-Broglie theory that matter has wave like behaviour.
BRAGG’S LAW IN X-RAY DIFFRACTION:
Two beams with identical wavelength and phase approach a crystalline solid and dissipated off two different atoms within it.The lower beam crosses an additional a length of 2ⅆ sinθ . Constructive interference happens when this length is equivalent to an integral multiple of the wavelength of radiation .Bragg peaks(very strong intensities) are gotten in the diffraction pattern where the scattering angles fulfill Bragg’s condition.
CONCLUSION:
The experimentally measured wavelength and the value estimated from de-Broglie hypothesis are in straight coincidence showing the existence of de-Broglie waves.
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