It is said that the Nobel Prize Committee of the Royal Swedish Academy of Sciences made an exception at the end of November 1922 to announce two awards at the same time: one was to award the 1921 Nobel Prize in Physics to physicist Albert Einstein for explaining the photoelectric effect.
The second is to award this year's Nobel Prize in Physics to physicist Bohr for his study of the atomic structure of the microscopic world and the theory of atomic models.
Immediately after the Nobel Committee awarded them the prize, it locked up the list of candidates for the 1923 Physics Prize: Robert Andrew Millikan, an American who had made a major breakthrough in the microscopic world of electrons and the interpretation of the photoelectric effect.
Nobel Prize-winning Millikan Image source: Physics Bimonthly Network
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Rich children are multi-talented
Millikan's ancestors lived in New Zealand, and his parents moved to Illinois, USA. As the second son in the family, Millikan received a good education, and his chinese and math scores were excellent in elementary school, and he belonged to "someone else's child". This laid a good foundation for his future development in many aspects.
After entering Obersen University in Ohio, he studied Greek and mathematics and then physics. In his sophomore year, he was appointed as a teacher in a pre-physics class, teaching while teaching on his own. Similar to the middle school teachers and students in the mainland in the 1980s and 1990s, junior high school graduates who teach junior high school students must be excellent students among eugenics.
Oberson University did not have physics textbooks, and Millikan volunteered to write a set of basic physics textbooks. This textbook was easy to understand and well-written, and was used by many schools, and Millikan began to emerge.
After college, illinois newspapers needed a reporter familiar with the law, and Millikan was invited to help. He incorporated his legal knowledge into his articles, and wrote humorous and pertinent reports.
While a journalist, he was commissioned as a juror or defense lawyer and performed very well in court. Since then, Millikan has gained fame in his hometown.
If this development continues, Millikan will become a brilliant professor, author, or lawyer, but it will be difficult to win the Nobel Prize in Physics. However, from the time he taught physics, he knew what he liked and where he should work. This is called self-knowledge.
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Oil drops test to measure charge
In 1895, after a brief stay in his hometown, the 27-year-old Millikan traveled to Europe at his own expense to study physics. After returning to the United States the following year, he enrolled at the University of Chicago to teach physics, and was soon promoted to associate professor for his outstanding teaching. In 1921, he transferred to caltech as head of the department of physics until his retirement in 1946.
While teaching at the University of Chicago, Millikan developed a keen interest in the microscopic world of matter and came up with the idea of determining the electrical charge of electrons.
Millikan is doing experiments Image source: Physics Bimonthly Network
Man's exploration of the microscopic world made a major breakthrough at the end of the 19th century: the British scientist J. J. Thomson was the first to experimentally prove the existence of electrons and measured the ratio between their charge and mass. This move breaks the centuries-old mainstream assertion that atoms are indivisible.
Since then, J· J. Thomson worked with his colleagues, townsend, Wilson, and others to measure electron charges. Because only by measuring the amount of charge of an electron can its mass, motion trajectory, etc. can be estimated. Unfortunately, little progress has been made.
In 1906, Millikan officially used Wilson's cloud chamber to measure the amount of charge of electrons in water. However, the results of the experiments that varied greatly again and again gave him a headache.
A few years later, he discovered that the reason for the large variation in measurement results was the rapid evaporation of water droplets, and thus invented the balanced water droplet method. This method is to energize the water droplets in the cloud chamber, generate a reverse electric field force, make the water droplets suspended, and slow down the evaporation rate. After repeated experiments, Millikan found that the differences between the experimental data were only reduced and did not solve the actual problem.
What to do? When the mountains were exhausted, Harvey Fletcher, a graduate student who worked with him, asked if he could replace the water droplets with other liquids. After careful consideration, Millikan decided to replace the water droplets with oil droplets and redesign the experiment.
He first used two horizontally arranged metal plates (or battery packs) as positive and negative electrodes, and the metal plates were equipped with two small holes, one of which was connected to the sprayer, which was responsible for spraying oil droplets into the internal device, and the other was a microscope observation hole. The oil droplets sprayed into the plate are charged by friction, overcome the gravitational rise under the action of the electric field force, and suspend in the air.
The assistant adjusts the voltage so that the oil droplets fall smoothly through the small holes to the observation area to keep the voltage constant, and the Millikan observes through the microscope.
Oil drop experiment diagram
After hundreds of observations, Millikan found that the total charge of all the oil droplets floating into the observation area was an integer multiple of the same number. "This minimum charge value is the electron charge!" He felt that he had found a breakthrough direction.
In order to get the data accurate, he and Fletcher took turns, carefully observing and recording the movement of individual charged oil droplets, often staring at the oil droplets for several hours, which was very hard.
In April 1912, Millikan calculated the amount of electricity e = (1.5924± 0.0017) of the basic charge through conclusive experimental data×10-19 coulombs, which is only 1% different from today's measurements e = 1.602176634 × 10-19 coulombs.
The following year, Millikan published a paper formally proposing that "any amount of electricity is an integer multiple of the fundamental charge."
Miligan Oil Drop Experiment Detailed Image Source: Physics Bimonthly Network
The basic charge is the smallest amount of electricity that exists in nature measured by experiments, and its appearance allows many physical constants to be calculated to achieve greater precision. Millikan also became famous.
Unfortunately, Millikan made two mistakes in his paper, which led to him and his oil drop experiment being criticized by posterity. First, the paper does not sign Fletcher's name; second, the article only lists 91 sets of observations, and does not mention a single word for the 49 groups that are quite different, which is seriously inconsistent with what the paper says that "all oil droplet experiments are represented" (see the Milligen Experiment Record).
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Research photoelectric surprise
Middle-aged Millikan's energy is quite energetic. When Fletcher was thinking about oil droplet experiments, he burst out with an idea: to prove that Einstein's quantum theory of light and the equation of photoelectric effects were wrong through experiments.
After Einstein proposed the quantum theory of light in 1905 and established the photoelectric effect equation, according to the view of the time, it was quite difficult to verify the photoelectric effect equation by directly measuring the photocurrent accurately through experiments, but only when the theory and experiment were combined, the new theory would be established.
It was only because Einstein's quantum theory of light was so careful that the photoelectric effect equation was not wrongly calculated, so most of the scientists at that time agreed with his theory, and only a small number of people, including Millikan, were skeptical.
Experiments to prove the quantum theory of light are more difficult than oil droplet experiments, after all, oil droplets are tangible and similar, but light cannot be grasped. Millikan began research in 1908 and knew that it was only in 1912 that the basic experimental apparatus was designed.
However, in the experiment, he gradually accepted Einstein's light quantum theory, and in 1915, he finally designed a set of ingenious devices to confirm the photoelectric effect equation and calculate the value of Planck's constant h.
Millikan Optical Quantum Experiment Source: Physics Bimonthly Network
In 1916, Millikan published the contents of his research. Since then, Einstein's quantum theory of light has been verified, and Millikan has won the 1923 Nobel Prize in Physics for his outstanding research.
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