Into Unscientific

  Chapter 260 Witness a miracle! (Down)

   "Catch a wave in an electromagnetic field?"

   Hearing Xu Yun's words.

   Faraday turned his head subconsciously, and exchanged glances with his good friend William Weber.

   Then the two electromagnetism masters thought of something at the same time.

   They shifted their gazes to the huge galvanized metal plate in the classroom.

   is different from ordinary visible light.

  If there is a wave in the electromagnetic field, it must have the property of being invisible to the naked eye.

  This is a truth that children understand. After all, if electromagnetic waves can be seen, Faraday and others have already noticed this thing.

  Therefore, Xu Yun's "grasp" must not be directly presenting the electromagnetic wave in front of everyone, but using a certain phenomenon or reaction as evidence.

   Just like Faraday’s iron filing experiment:

  At that time, he sprinkled a layer of extremely fine iron filings on a piece of paper, put a magnet under the paper, and then tapped the paper lightly.

  Thus, the shaken iron filings are neatly arranged along the magnetic lines from the north pole to the south pole of the magnet.

  Faraday thus discovered the concept of lines of magnetic force.

   Therefore, if nothing unexpected

  Xu Yun's 'capture' this time is obviously replacing the real thing with phenomena, which is definitely not surprising.

   But what will happen?

   is a physical reaction?

   Or replace the invisible with phenomena?

   While Faraday and the others were thinking, Xu Yun spoke again:

   "Professor Faraday, can we start the experiment now?"

  Faraday came back to his senses, and cast a questioning look at Prince Albert at the side.

  Although the uncrowned king of the British Peninsula lacks professional knowledge, he is the person with the highest status on the scene after all, and the experiment must obtain his consent before it can start.

  Pro-Albert Faraday nodded slightly, and said to Xu Yun:

   "Please start, Luo Feng."

  Xu Yun said yes, and glanced at Prince Albert lightly from the corner of his eye.

  In the few short words just now, Prince Albert paused twice, and the pause was accompanied by swallowing movements.

It is clear.

  The stomach and esophageal spasms that eventually led to Prince Albert's untimely death had already had relatively clear symptoms.

  Albert, as the most famous "husband-in-law" in British history, later generations, especially British medical scientists, have done a lot of research on his condition before his death.

   To be sure.

  Prince Albert suffered from waist rheumatism, prostatic hypertrophy, stomach cramps and reflux esophagitis during his lifetime.

  The last two of them are most likely to be the culprits that lead to the death of Prince Albert.

  There is no omeprazole in the UK these days, and reflux esophagitis is much higher than later generations in terms of pain and threat.

   But Xu Yun hesitated.

  He wasn't sure if he should make a move.

  Because in the original history of Prince Albert, his attitude towards China was too strange and too strange.

   First of all, as an interest class, Prince Albert must have enjoyed the dividends that a crow brought to Britain.

  But as the uncrowned king of Britain, he himself has never expressed any attitude or instructions to Huaxia.

  He did not care about the situation in the East from the beginning to the end, and his focus was mainly on Germany, America, industry and economy during his lifetime.

  As if the East does not exist at all, the prime minister of the United Kingdom has always been in charge of the strategy towards China.

  In his previous life, Xu Yun asked a friend to help him collect the scanned version of the British China Bill from 1840 to 1865. He spent more than 700 yuan, but he didn't find even a bill decided by Albert.

   Not to mention good or bad character, this is completely unreasonable from the perspective of a country's decision-makers—any European class, who would ignore China in the 19th century?

  But Albert did just that.

  It’s like you have a stock software that gives you tens of millions of dividends and interest a year, but you never care about this part of the money, and you don’t even have the idea of ​​turning on your mobile phone to see how much it has risen yesterday.

   This is obviously a very, very strange behavior.

  The Jinling University of later generations even opened a project on this, studying Prince Albert's attitude towards China, but in the end there was no accurate conclusion.

  So Xu Yun really doesn't understand what kind of character this person is.

  If it were a villainous foreign gun team captain like Grant, or a respectable international friend like Lindsay, it would be much easier to deal with.

  Think here.

  Xu Yun couldn't help shaking his head, and put this thought behind him.

   It's still a long time, so let's take a look at it slowly.

  The top priority now is to deal with the experiment and connect Faraday's line.

   Then he walked to the side of the experimental generator and said to Thomson:

   "Mr. Thomson, please pull down all the curtains in the room."

  Thomson nodded immediately and said:

"clear."

  Swipe la la—

   After a while.

  All the black curtains in the classroom were drawn down.

  In addition, the classroom is located in a remote corner, so the room is not completely dark at this time, at least it can be regarded as the standard of a 'dark room'.

  Xu Yun checked the equipment one last time, and then pressed the switch of the equipment.

  Compared with yesterday's experiment, the generator prepared by Xu Yun today has more detailed specifications:

  The copper ball remains unchanged, but the length of the copper rod connecting the copper ball remains constant at 12 inches, and the side length of the square zinc plate is 16 inches.

soon.

  ZiZiZi—

   As the voltage increased, the spark reappeared.

   Whoosh—

   Immediately after.

  With the reflection of light, sparks appeared on the receiver at the same time.

  See this scenario.

   Faraday and the others looked at each other again, and a trace of doubt flashed in their pupils.

  The phenomenon is still shocking, but it seems

   Is there any difference from yesterday's?

   But soon.

  Faraday's attention was attracted by something in Xu Yun's hand:

  It was a glass tube about the size of a flashlight, and there was some black powder inside, which looked a bit like sesame powder.

  There is a wire outside the glass tube, and the two ends of the wire are connected to the two ends of the glass tube correspondingly to form a loop, and a voltmeter is hung on one end.

  Seeing this, Faraday couldn't help standing up, walked to Xu Yun, and pointed to the glass pipe:

   "Student Luo Feng, what is this?"

  Xu Yun glanced at him, raised the glass tube, and explained with a smile:

   "This is a chip detector."

   "Swarf detector?"

  Faraday repeated the word several times, and suddenly thought of something.

  I saw him suddenly raised his head, and looked at the huge galvanized metal plate fixed on the wall.

after awhile.

  He looked at Xu Yun with emotion on his face, and said clearly:

   "So that's it. I see, it's standing waves. Mr. Fat Fish used standing waves, right?"

  Xu Yun smiled and nodded.

   Well known.

  The photoelectric effect is an extremely shining node in the history of physics. It has many theoretical derivations, but in the conceptual sense, there are only two main points.

  First of all, it refuted the wave theory of light—it gave three blows to the main artery of the wave theory.

  The first knife is the cutoff frequency.

   That is, for a certain metal material, only when the frequency of the incident light is greater than a certain frequency v0, electrons can escape from the metal surface to form photocurrent.

   This frequency v0 is called cut-off frequency, also known as red limit frequency, limit frequency.

  If the frequency v of the incident light is less than the cut-off frequency v0, no matter how strong the incident light is, the photoelectric effect cannot be produced.

   According to the point of view of wave optics.

  No matter what the frequency is, as long as the light is strong and the time is long, the electrons can gain enough kinetic energy to leave the cathode.

  The second knife cannot explain why there is a cut-off voltage, and it only changes with frequency:

  According to the viewpoint of wave optics, the kinetic energy of the electrons leaving the cathode should be proportional to the light intensity and irradiation time.

   Therefore, the upper limit of electron kinetic energy should change with light intensity and irradiation time, that is, the cut-off voltage will change with light intensity.

  The third knife is the problem of instantaneousness - even if the light is very weak, the response time of the photoelectric effect is still very fast, and it does not change with the light intensity.

  According to the point of view of wave optics.

  Under a specific cut-off voltage, the photoelectric effect time should be inversely proportional to the light intensity.

  But in fact, no matter what the light intensity is in the photoelectric effect, as long as the cut-off frequency and cut-off voltage requirements are met, the generation time of the photoelectric effect is on the order of 10e-14s.

   But still that sentence.

  In 1850, the scientific community’s understanding of the microscopic field was still too narrow, so Xu Yun was not going to explain the truth of the entire photoelectric effect at this time.

   No one knows the answer, so it can be called a dark cloud.

  He is just an ordinary porter who has done a little work, so please ask someone else to answer the question.

  In addition to the theory of anti-killing fluctuations.

   Another conceptual significance of the photoelectric effect is to verify the existence of electromagnetic waves.

To know.

  If you only look at the photoelectric effect phenomenon itself, it is not enough to support the electromagnetic wave or the conclusion that "the primary coil electromagnetically oscillates and the secondary coil is induced".

  So how did Hertz verify electromagnetic waves?

  The answer is the standing wave method.

  Simply speaking, standing waves Standing waves are waves that cannot go away.

  Will Lai stay there?

   Of course, it is between two opposite parallel walls.

  A space has three sets of opposing parallel walls, that is, front and back, left and right, and up and down.

  Its essence is the resonance phenomenon of space, and the comprehensive equation is y=y1+y2=2Acos2π(x/λ)cos2π(t/T).

   It is not difficult to see from this equation.

  The pitch of a standing wave is equal to n times the half wavelength, so the original wavelength can be calculated as long as the pitch is known.

  In this way, the problem of verifying electromagnetic waves can be attributed to another new link:

  How to determine the pitch?

   In 1887, Hertz gave the answer with an exquisite design:

  He first arranged a secret room, and then designed a detector composed of the principle of a radio wave ring, and used the detector to detect standing waves.

   This detector won't display numbers, but can emit sparks depending on the situation:

  Wave has crests and troughs. The detector has the brightest flame when it is in the peaks and troughs, and there is no flame when the value is 0 between the peaks and troughs.

   From this, the pitch of the standing wave can be obtained by calculating the position you are standing on.

Of course.

   Hertz’s geophone is relatively primitive and its sensitivity is very low, so Xu Yun made some modifications on the geophone this time:

  He made a chip detector.

   When the photoelectric effect does not occur, iron filings are loosely distributed.

  The entire geophone is equivalent to an open circuit, and the ammeter will not display the current.

   And once the electromagnetic wave is detected.

  The iron filings will move, gather into a ball, play the role of a conductor, and activate the voltmeter.

  The closer to the peak or trough, the more iron filings will condense, and the greater the value on the meter will be.

   In this way, it is undoubtedly much clearer and more precise than naked eye observation.

   In a sense.

  This is also the most attractive part of the subject of physics.

  Sometimes you don’t need any equipment accurate to the femtometer nanoscale, the idea is the most important.

  Like when Xu Yun was in school, there was an experiment that needed to simulate the vibration of spider silk, but he couldn't find equipment with a suitable vibration period for a while.

   As a result, a female man took out the X stick and X protector on the spot, and perfectly simulated the required cycle data through the sponge pad.

   That matter once became a legend of the University of Science and Technology, and Xu Yun and the others even mentioned it when they were reunited.

Of course.

  Xu Yun and the others haven’t made it clear to that girl all the time—afterwards everyone thought about it, and in fact, the practical razor is almost the same

  Ahem, let’s get down to business.

  The idea is clear, and the rest is very simple.

  Xu Yun kept the generator in the activated state, and distributed several detectors prepared by William Whewell to everyone, and started to detect the standing wave.

   "The voltmeter here is 0, which is a zero point!"

   "Is there anything bigger than mine at 1.7V?"

  “.Should be gone, 1.7 seems to be where the peaks and troughs are.”

   "1.51.61.7, found, my place is a peak area!"

  The voices of a group of bigwigs echoed in the room, and soon, the pitches of several standing waves were detected.

   "0.26 meters."

  Looking at the statistically compared values, Faraday touched his chin:

   "The distance between two points where the standing wave cancels is half the wavelength, that is, nλ/2. Then, if calculated in this way, the wavelength of the electromagnetic wave is"

   "6.5×10^-7m?"

  Xu Yun nodded.

  There are actually two main spectral lines of the photoelectric effect, one is 6.5×10-7m, and the other is 4.8×10-7m.

   These scales can be easily measured in the macroscopic world after being magnified by standing waves.

   In other words.

  Xu Yun really 'captured' the electromagnetic wave!

  Looking at the value on the paper, and then at the detector in his hand.

  While Faraday was shocked and admiring, he couldn't help feeling a little bit depressed:

  Although he already knew that he could not compare with Mr. Fat Fish, he never expected that the gap between himself and Mr. Fat Fish would be so big

  This experiment that Mr. Fat Fish casually designed is probably enough for everyone present to reminisce for a lifetime.

   Not to mention according to Xu Yun.

  This is just one of the experiments designed by Mr. Fat Fish.

   As expected of a character who can stand alongside Sir Newton.

all in all.

   Things have come to this point, the next thing is very simple.

  These days Hertz has not proposed the concept of the frequency unit, that is, Hertz.

   But the spectrum thing was invented as early as the Mavericks period, but it is still relatively close to the "period" in definition.

  The generator designed by Xu Yun is equivalent to an oscillating dipole, which will excite high-frequency oscillations during the occurrence, and the induction coil will be charged at a frequency of 10-100 per second, resulting in a damped oscillation pattern. (I'll try again to see if I can put it in this chapter. Now the review in this chapter is a bit speechless)

  Knowing the number of turns and power, the cycle calculation is very simple.

   So fast.

  The two values ​​of wavelength and oscillation period were placed in front of Faraday and others at the same time.

  Faraday stared at the value for a long time, finally picked up the pen and started the calculation.

  The frequency of the electromagnetic wave is the same as the oscillation frequency of the wave source, and the wavelength is related to the refractive index of the medium.

  Although the refractive index in air is not the same as in vacuum, for everyone in 1850, this error can basically be ignored.

   Swish Swish Swish—

  Faraday's pen tip moved steadily and quickly across the paper.

  He is not very good at mathematics, and he will feel a little bit strenuous in the face of the current amount of calculations.

After a few minutes.

  Faraday finally calculated the last digit.

   Just when he was about to breathe a sigh of relief, his brow subconsciously frowned again.

Do not know why.

  He always felt that the number on the paper seemed familiar?

  Seeing Faraday's expression of hesitation, Xiaomai beside him couldn't help it. This person's thirst for knowledge is even comparable to that of a calf.

  I saw him rushing forward to take a few glances, and suddenly let out a light sigh:

   "2.97969X10^8m/s, this is not"

   "The speed of light?!"

   It’s been a long time since I asked for a monthly pass. Can you call me for a monthly pass? It’s not doubled at the end of the month! !

  (end of this chapter)