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Topik: Fizik Quantum


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Oleh Fizik Quantum

Saifuddin
WARGA SETIA
Menyertai: 30.09.2003
Ahli No: 3878
Posting: 1421

Kelantan  


posticon Posting pada: 04-12-08 10:26


assalamualaikum
mari kita bincang hal fizik quantum...

In physics, a quantum (plural: quanta) is an indivisible entity of a quantity that has the same units as the Planck constant and is related to both energy and momentum of elementary particles of matter (called fermions) and of photons and other bosons. The word comes from the Latin "quantus," for "how much." Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. There is a related term of quantum number.

A photon is often referred to as a "light quantum." The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general. But these terms can be a little misleading, because what is quantized is this Planck's constant quantity whose units can be viewed as either energy multiplied by time or momentum multiplied by distance.

Usually referred to as quantum "mechanics," it is regarded by virtually every professional physicist as the most fundamental framework we have for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.

Quantum theory, the branch of physics which is based on quantization, began in 1900 when Max Planck published his theory explaining the emission spectrum of black bodies. In that paper Planck used the Natural system of units he invented the previous year. The consequences of the differences between classical and quantum mechanics quickly became obvious. But it was not until 1926, by the work of Werner Heisenberg, Erwin Schrödinger, and others, that quantum mechanics became correctly formulated and understood mathematically. Despite tremendous experimental success, the philosophical interpretations of quantum theory are still widely debated.

Planck was reluctant to accept the new idea of quantization, as were many others. But, with no acceptable alternative, he continued to work with the idea, and found his efforts were well received. Eighteen years later, when he accepted the Nobel Prize in Physics for his contributions, he called it "a few weeks of the most strenuous work" of his life. During those few weeks, he even had to discard much of his own theoretical work from the preceding years. Quantization turned out to be the only way to describe the new and detailed experiments which were just then being performed. He did this practically overnight, openly reporting his change of mind to his scientific colleagues, in the October, November, and December meetings of the German Physical Society, in Berlin, where the black body work was being intensely discussed. In this way, careful experimentalists (including Friedrich Paschen, O.. Lummer, Ernst Pringsheim, Heinrich Rubens, and F. Kurlbaum), and a reluctant theorist, ushered in a momentous scientific revolution.


The quantum black-body radiation formula
When a body is heated, it emits radiant heat, a form of electromagnetic radiation in the infrared region of the EM spectrum. All of this was well understood at the time, and of considerable practical importance. When the body becomes red-hot, the red wavelength parts start to become visible. This had been studied over the previous years, as the instruments were being developed. However, most of the heat radiation remains infrared, until the body becomes as hot as the surface of the Sun (about 6000 K, where most of the light is green in color). This was not achievable in the laboratory at that time. What is more, measuring specific infrared wavelengths was only then becoming feasible, due to newly developed experimental techniques. Until then, most of the electromagnetic spectrum was not measurable, and therefore blackbody emission had not been mapped out in detail.

The quantum black-body radiation formula, being the very first piece of quantum mechanics, appeared Sunday evening October 7, 1900, in a so-called back-of-the-envelope calculation by Planck. It was based on a report by Rubens (visiting with his wife) of the very latest experimental findings in the infrared. Later that evening, Planck sent the formula on a postcard, which Rubens received the following morning. A couple of days later, he informed Planck that it worked perfectly. At first, it was just a fit to the data; only later did it turn out to enforce quantization.

This second step was only possible due to a certain amount of luck (or skill, even though Planck himself called it "a fortuitous guess at an interpolation formula"). It was during the course of polishing the mathematics of his formula that Planck stumbled upon the beginnings of Quantum Theory. Briefly stated, he had two mathematical expressions:

(i) from the previous work on the red parts of the spectrum, he had tak;
(ii) now, from the new infrared data, he got tak².
Combining these as tak(a+tak), he still has tak, approximately, when tak is much smaller than a (the red end of the spectrum); but now also tak² (again approximately) when tak is much larger than a (in the infrared). The formula for the energy E, in a single mode of radiation at frequency λ, and temperature T, can be written


This is (essentially) what is being compared with the experimental measurements. There are two parameters to determine from the data, written in the present form by the symbols used today: h is the new Planck's constant, and k is Boltzmann's constant. Both have now become fundamental in physics, but that was by no means the case at the time. The "elementary quantum of energy" is hλ. But such a unit does not normally exist, and is not required for quantization.
untuk info lanjutan...click
http://en.wikipedia.org/wiki/Quantum

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Daeng_Jati
-WARGA AMAT SETIA-
Menyertai: 17.02.2004
Ahli No: 7336
Posting: 9704
Dari: UKM, Bangi

brunei   avatar


posticon Posting pada: 04-12-08 11:51


terima kasih Saifuddin di atas ilmu Fizik Kuantum ini. Amat menarik bila sekecil2 benda ciptaan Allah SWT manusia kaji...

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Daeng_Jati
-WARGA AMAT SETIA-
Menyertai: 17.02.2004
Ahli No: 7336
Posting: 9704
Dari: UKM, Bangi

brunei   avatar


posticon Posting pada: 04-12-08 11:53


Saya pun nak berkongsi dengan ilmu Fizik Kuantum ini.

Berdasarkan teori cahaya foton, foton adalah bondongan diskrit atau lebih dikenali sebagai kuantum tenaga elektromagnetik (cahaya). Foton sentiasa dalam gerakan dan mempunyai kelajuan cahaya yang malar di dalam vakum, c = 2.998 tak 108 m/s.

Sifat asas foton;

1) Bergerak pada kelajuan yang malar
2) Tidak mempunyai jisim
3) Membawa tenaga dan momentum yang berkaitan dengan frequensi dan panjang gelombang.
4) Boleh dimusnah dan dicipta apabila radiasi diserap atau dibebaskan.
5) Mempunyai interaksi seakan zarah contohnya perlanggaran dengan elektron.

Dalam fizik, foton adalah elemen zarah yang bertanggungjawab kepada fenomena elektromagnetik. Ia membawa radiasi elektromagnetik bagi semua panjang gelombang seperti sinar gamma, sinar tak, Ultraungu, cahaya nampak, inframerah, mikrogelombang dan gelombang radio. Foton berbeza dengan elemen zarah yang lain kerana ianya tidak mempunyai jisim. Oleh itu foton bergerak dalam vakum dengan kelajuan cahaya. Foton mempunyai gelombang dan sifat zarah (wave-particle-duality). Foton menunjukkan fenomena gelombang boleh memantul walaubagaimanapun sebagai zarah ia hanya boleh berinteraksi dengan jirim dengan perpindahan tenaga.

E = hc/λ

h = pemalar Planck
c = kelajuan cahaya
λ = panjang gelombang


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Daeng_Jati
-WARGA AMAT SETIA-
Menyertai: 17.02.2004
Ahli No: 7336
Posting: 9704
Dari: UKM, Bangi

brunei   avatar


posticon Posting pada: 16-12-08 20:50


saaya ingin bertanya tentang dua (2) bidang ini iaitu Teori Relativiti dan Mekanik Kuantum...

Apakah kaitan antara duanya? dan
Apakah pemisah antara duanya...

Teori Relativiti? teringat tentang permaidani empuk alam semesta
Mekanik Kuantum? teringat pula tentang kitaran planet mengelilingi matahari...

Keduanya membuatkan saya mengelamun...


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Daeng_Jati
-WARGA AMAT SETIA-
Menyertai: 17.02.2004
Ahli No: 7336
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brunei   avatar


posticon Posting pada: 16-12-08 20:52


Apa pula takrifan Teori String? yang mempunyai hubungkait lubang hitam?

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Rashdin
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Menyertai: 31.03.2004
Ahli No: 8143
Posting: 7868
Dari: dekat pada PC

uk   avatar


posticon Posting pada: 16-12-08 23:11


Pada 16-12-08 20:52 , Daeng_Jati posting:

!!! QUOTE !!!

Apa pula takrifan Teori String? yang mempunyai hubungkait lubang hitam?



ni dari wikipedia

String theory is a still-developing approach to theoretical physics, whose original building blocks are one-dimensional extended objects called strings. String theory attempts to reconcile quantum mechanics with general relativity in order to describe a quantum theory of gravity.

Since its birth as the dual resonance model which described the strongly interacting hadrons as strings, the term string theory has changed to include any of a group of related superstring theories which unite them. One shared property of all these theories is the holographic principle. String theory itself consists of many theories with different mathematical formulas. The logical coherence of the approach, however, and the fact that string theory can include all older theories of physics, have led many physicists to believe that such a connection is possible. In particular, string theory is the first candidate for the theory of everything, a way to describe all the known natural forces (gravitational, electromagnetic, weak and strong) and matter (quarks and leptons) in a mathematically complete system. On the other hand, many detractors criticise string theory because it has not yet provided experimentally testable predictions.

Like any other quantum theory of gravity, it is widely believed that testing the theory experimentally would be prohibitively expensive, requiring feats of engineering on a solar-system scale. Although some critics concede that string theory is falsifiable in principle, they maintain that it is unfalsifiable for the foreseeable future, and so should not be called science.

String theory is of interest to many physicists because of the mathematics involved, and because of the large number of forms that the theories can take. String theory strongly suggests that spacetime has eleven dimensions, as opposed to the usual three space and one time, but the theory can easily describe universes with four observable spacetime dimensions as well.

String theories include objects more general than strings, called branes. The word brane, derived from "membrane", refers to a variety of interrelated objects, such as D-branes, black p-branes and Neveu-Schwarz 5-branes. These are typically extended objects that source differential form generalizations of the vector potential electromagnetic field. All such objects are known to be related to one-another by a variety of dualities. For example, the black hole-like black p-branes are identified with D-branes, upon which strings end, through Gauge-gravity duality. Research on this equivalence has led to new insights on quantum chromodynamics, the fundamental theory of the strong nuclear force.



ni pula dari link lain

So what is the theory, then?
. Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension.
. In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings.
. In string theory, as in guitar playing, the string must be stretched under tension in order to become excited. However, the strings in string theory are floating in spacetime, they aren't tied down to a guitar. Nonetheless, they have tension. The string tension in string theory is denoted by the quantity 1/(2 p a'), where a' is pronounced "alpha prime"and is equal to the square of the string length scale.
. If string theory is to be a theory of quantum gravity, then the average size of a string should be somewhere near the length scale of quantum gravity, called the Planck length, which is about 10-33 centimeters, or about a millionth of a billionth of a billionth of a billionth of a centimeter. Unfortunately, this means that strings are way too small to see by current or expected particle physics technology (or financing!!) and so string theorists must devise more clever methods to test the theory than just looking for little strings in particle experiments.
. String theories are classified according to whether or not the strings are required to be closed loops, and whether or not the particle spectrum includes fermions. In order to include fermions in string theory, there must be a special kind of symmetry called supersymmetry, which means for every boson (particle that transmits a force) there is a corresponding fermion (particle that makes up matter). So supersymmetry relates the particles that transmit forces to the particles that make up matter.
. Supersymmetric partners to to currently known particles have not been observed in particle experiments, but theorists believe this is because supersymmetric particles are too massive to be detected at current accelerators. Particle accelerators could be on the verge of finding evidence for high energy supersymmetry in the next decade. Evidence for supersymmetry at high energy would be compelling evidence that string theory was a good mathematical model for Nature at the smallest distance scales.

http://www.superstringtheory.com/basics/basic4.html


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"It is better to dia for something than live for nothing" - Abraham Lincoln


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syahbi
Warga 4 Bintang
Menyertai: 08.03.2005
Ahli No: 14983
Posting: 250
Dari: Skudai

Johor  


posticon Posting pada: 17-12-08 01:41


Sapa boleh translate jadi bahasa melayu ke..atau bahasa yang lagi mudah...
Please...kita ini English tak pandai sangat lah ek

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alwalid
WARGA SETIA
Menyertai: 19.12.2004
Ahli No: 13142
Posting: 1229
Dari: seri iskandar

Perak   avatar


posticon Posting pada: 17-12-08 10:05


Pada 17-12-08 01:41 , syahbi posting:

!!! QUOTE !!!

Sapa boleh translate jadi bahasa melayu ke..atau bahasa yang lagi mudah...
Please...kita ini English tak pandai sangat lah ek


Salam alaik Syahbi,
patut saudara Syahbi gunekan ini sebagai latihan untuk kukuhkan lagi English anda, anda tak boleh harap semua orang akan spoonfeed awak sahaja........

kalau tak mula dari sekarang bila lagi????


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"Let Allah be the ruler over your hearts"


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syahbi
Warga 4 Bintang
Menyertai: 08.03.2005
Ahli No: 14983
Posting: 250
Dari: Skudai

Johor  


posticon Posting pada: 18-12-08 11:40


Haha...sebenarnya fahamlah ek.."iam being sarcastic ok"...tak faham ke?kalau saya nak tahu...boleh saja search google..tapi kan ada rakan-rakan kita dalam ukhwah ini yang kurang pengetahuan dalam english..Kenapa tak mudahkannya..kalau niat kita nak kongsi ilmu...biarlah dengan cara yang sebaik-baiknya...copy paste tak membantu


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"CaRiLaH KaSiH InsaN DemI CinTa TuHAn"


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Daeng_Jati
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Menyertai: 17.02.2004
Ahli No: 7336
Posting: 9704
Dari: UKM, Bangi

brunei   avatar


posticon Posting pada: 18-12-08 11:53


syabi, awak mahasiswa UTM ye? dalam bidang apa ya? boleh juga kita berkongsi ilmu....

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syahbi
Warga 4 Bintang
Menyertai: 08.03.2005
Ahli No: 14983
Posting: 250
Dari: Skudai

Johor  


posticon Posting pada: 20-12-08 01:51


Saya bidang kejuruteraan elektrik,Pasal fizik kuantum memenag tak tahu apa-apa lah saya ini...haha

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