Hello Friends, In this blog i going to provide of short note of
Helium-
Neon Laser it's
properties application. it's stable and meta stable state and also explained about
Heisenberg's uncertainty principle.
Heisenberg's Uncertainty Principle
The uncertainty principle was proposed by Heisenberg in 1927. This principle is a direct of cording to classical mechanics, a moving particle has a definite momentum definite position in space and it is possible to determine both its position and velocity.
in quantum mechanics a moving particle is described by a wave group (wave packet) so the particle may a small wave group, the position of the particle can be fixed but the particle will spread rapidly and hence the velocity becomes uncertain. On the other hand for a large wave group the velocity can be fixed but there is large, indefiniteness in position. In this way the certainly in position involves uncertainty in momentum or velocity and certainty of momentum involves the uncertainty in position. This shows that it is impossible to know where within the wave group, the be located anywhere within the group at a given time. For particle is and what is its exact momentum.
Such type of uncertainty exists even in case of energy and time, angular momentum and angular displacement etc. So, the uncertainty principle may be stated as "it is impossible to determine simultaneously boih the member of a pair of variable that describe thie motion of an atomic system with accuracy and precession". Such variables are called canonically conjugate variables. If one of the variable is determined accurately, then there will be infinite error in the measurement of another variable.
If Ax and Ap be the uncertainties, in the measurement of position and momentum of a particle at the same time respectively then, the product of these uncertainties is equal to or greater than h/2pi
Laser is a contrivance (device) which produces a very intense, monochromatic, coherent and highly unidirectional beam of light. Laser is an acronym (short form) for Light Amplification by Stimulated Emission of Radiation. This is a concise description of what a laser does. The key to the 'light amplification process that is very rare in nature, the stimulated emission of a photon (radiation) by an atom in an excited state.https://www.azooptics.com/Article.aspx?ArticleID=464
Before the invention of laser, MASER was invented which abbreviated form of Microwave
Amplification by Stimulated Emission of Radiation and it produces such a beam of microwave. Theprinciple of MASER is identical to that of laser. Due to this reason, laser is also called optical MASER.
Now a days, IRASER (Infrared Amplification by Stimulated Emission of Radiation) and BASER (Boson).Amplification by Stimulated Emission of Radiation) have been developed. Fermions (to be discussed later)cannot be amplified using the principle involved in these devices.
C.H. Towns, N. Basov and A.P. Khorov in 1958, worked out the theory of laser. They were jointly awarded Noble Prize in 1964, for the same. The laser was developed in 1960. Laser can be generated in gaseous,solid and liquid media. Ruby laser is a solid type laser, Helium laser, Neon laser etc. are gaseous lasers.
Stable and Metastable State
Usually an atom in its ground state is said to be stable. When energy is supplied to such atoms they jump
to the higher energy states which we call excited states. The life time of such states is very short of the
order of 10-8s. But, the life time of some excited states are relatively longer of the order of 10-3. Such states
are called metastable states.
Principle of Laser
With the help of optical pumping, a large number of electrons are raised to meta-stable state. In this state han induced abs n induced absorption by the lower state. Under this condition a strong and coherent beam of photons f same frequency is produced in which all photons have the same phase and direction. These photons combine to produce a single light wave light i.e laser light. This is the principle of laser that underlies the operation of the laser.
With the help of optical pumping, a large number of electrons are raised to meta-stable state. In this state han induced abs n induced absorption by the lower state. Under this condition a strong and coherent beam of photons f same frequency is produced in which all photons have the same phase and direction. These photons combine to produce a single light wave light i.e laser light. This is the principle of laser that underlies the operation of the laser.
Helium Neon laser
RUBY laser is the first laser developed in
1960. It is a solid type laser and is a three
level laser. The output beam is not
continuous though very intense in this
three level laser. So, a four level laser
was developed for continuous output
laser beam which is He Ne laser.
It consists of a discharge tube of nearly 0.5 m length and diameter about 5mm whose two ends are cut at Brewster's angle. The tube is filled with the mixture of helium and neon in the ratio 5:1 at a total pressure of about 1 torr. The tube is also provided with two parallel mirrors at the ends, one of which is 100%reflecting and while the other is partially transparent. The distance between the mirror is half integer multiple of the wavelength of laser light.
Application of Laser
.
i. In telecommunication: Due to high coherency, laser beam can be sent to long distance without much loss of energy. Due to higher carrier frequency in laser beam, their band width is broad. So, millions of channels can be transmitted on a single laser carrier wave. It has also become possible to have holographic T.V. pictures using laser. It is being used to send messages to moon and under water using laser beam. The under-water communication between submarines is also possible by laser.
2. In medical science: laser beam is used in bloodless surgery. It is used to prevent decay of teeth by minerals on the dental surface, drilling of teeth, removal of tumors, retinal surgery
and removing of infected cells and their parts.
3. inustry: Due to high energy concentration per unit area of cross section of the beam, laser cn
produce temperature of the order 10* C and are used for drilling holes, fusing or melting
or cutting thick metal sheet.
4.In measurement of long distance: As lasers have no angular spread they are used to measure long
distances (for example, the distance of moon from the earth) by echo-method
5. In weather forecasting: It is used to take clear pictures of the clouds and to measure variation in
atmospheric pressure for weather forecasting.
6. For national defence: It is used for controlling and guiding space rockets and satellites, locating of
planes etc.
7. In war: It can be used as a weapon in war. A laser beam focused on tanks and planes can damage
them. During war time, lasers are used to detect and destroy the enemy missiles. Now, laser rifles,
laser pistols and laser bombs are also being made which can be aimed at the enemy in the night.
8. Laser is used for three dimensional photography (holography)
9. Laser is used in detecting nuclear explosion and earthquakes, in vaporizing solid fuel of rockets, in
the study of the surface of distant planets and satellites.
10. It is used to determine the temperature of plasma and density of electron.
11. Laser-torch is used to see objects at long distances.
12 It is used to take photograph of fast moving objects.
13. It is used to study the molecular structure and nature of a chemical reaction.
Properties of Laser
i. Laser can travel over long distance without much loss of energy (or intensity).
ii.. It is highly monochromatic
iii. It is highly unidirectional beam of light.
iv. It is coherent i.e. all atoms emit radiations simultaneously
v. It is very intense.
vi. Its wavelength is very, very short.
vii. It is highly energetic light.
vii. It stays on at a single frequency.
ix. It is well acclimated i.e. all rays are perfectly parallel to each other. Hence, a laser beam is very
narrow and can travel to long distance without spreading. It can be brought to an extremely sharp
focus.
x. It can vaporize even the hardest metal because of its high energy density and directional propert
laser beam can produce temperature of order of 104 oC at a focused point.
Ordinary light
1. It is less intensive than laser
2. It is chromatic
3. It is multidirectional.
4. It is incoherent source.
5. Wavelength is longer than laser.
6. Less energetic than laser
7.It consists of many wavelength and It has only a particular frequency.
8. It can produce ordinary temperature But, it produces high temperature in order of
when strikes on an object.
Significance of Uncertainty Principle in Our Daily Life
One of the important implications of the Heisenberg's uncertainty principle is that, it rules out the well
proposed by Bohr. Since, for a subatomic particle like angoodctory of an electron or well defined(orbits)
or trajectories electron, it is not degree of precision, therefore, it is not possible to talk about the trajepossible
circular orbits.
It should be born in mind that, the uncertainty is not due to lack of sufficiently defined techniques but,itis
due to the fact that, we cannot observe microscopic things without disturbing them. No instrument can
observe the position of an electron without affecting its motion. In other words, uncertainty principle is the
fundamental limitation of nature. Thus, we cannot design an experiment to obtain an accurate value of b
the position and momentum for microscopic objects.
However, in our daily life, this principle has no significance. This is because, we come across only large
objects, i.e., the objects which we can observe with naked eyes without altering their motion. The position
and velocity of these objects can be detcrmined accurately because in these cases, during the interaction
between the object and the measuring device, the changes in position and velocity are negligible.
