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Table of Content
20 July 2018 Volume 37 Issue 7
Ultrashort pulse laser and optical frequency comb
ZHOU Jing
College Physics. 2018, 37(7): 1-4. doi:
10. 16854 /j. cnki. 1000-0712. 170596
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Qualitative and semi - quantitative analysis on the ultrashort pulse laser and optical frequency comb is made using the wave interference theory and Fourier transformation. Based on the known conclusions about the multiple beam interference，we analyze the principle of mode locking technology，the temporal characters of pulse laser. Using the Fourier transformation and Fourier series，we demonstrate the physical image of the optical frequency comb，derive the relation between the pulse length and the spectral bandwidth，the relation between the temporal pulse distance and the spectral frequency interval.
An experiment to explain the wave - particle duality and quantum entanglement of quantum mechanics
LIU Ying，CHANG Chun-rui，WEI Huan，GU Jian-sheng
College Physics. 2018, 37(7): 5-7. doi:
10. 16854 /j. cnki. 1000-0712. 180023
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2317
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617
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The anticoincidence experiment is analyzed deeply and used to explain some basic principles of quantum mechanics approachable. Like the classical physics，basic principles of quantum mechanics such as wave - particle duality，superposition principle and quantum entanglement are also irrefutable experimental results.
On the stability and critical charge of charged droplets
YU Feng-jun
College Physics. 2018, 37(7): 8-10. doi:
10. 16854 /j. cnki. 1000-0712. 170481
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1840
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1024
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For two charged models for charge distribution in the droplet surface and in the droplet，the stability of charged droplets is discussed by using energy analysis method，and the expression of the critical charge is derived.
Calculation of electric field and capacitance between confocal hyperbolic cylinders by complex potential function
JIA Xiu-min
College Physics. 2018, 37(7): 11-14. doi:
10. 16854 /j. cnki. 1000-0712. 170594
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1602
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By using the properties of the analytic function，the electric field and the capacitance per unit length between the confocal hyperbolic cylinders are derived by the inverse hyperbolic sine function and the boundary condition，and some special conductor configurations are also discussed.
The Green's function method based on conformal mapping and its pplication
WANG Fu-qian，YIN Yong，LIU Wei-qi
College Physics. 2018, 37(7): 15-18. doi:
10. 16854 /j. cnki. 1000-0712. 170442
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1925
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421
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The two - dimensional ( 2D) boundary value problem of the complex shape boundary is solved by combing the Green's function method and conformal mapping. Meanwhile the distribution of electric field is got.Both the electric field line and equipotential line maps are plotted by using mathematical software MATLAB，thus the validity of the method in the paper is presented. The application range for the Green's function method is expanded，and a novel idea and way is provided for solving the complex shape boundary 2D electrostatic field boundary value problem.
A simplified determination of atomic ground state under the circumstance of the LS coupling
LU Tong-suo1，2，SUN Min3，HUANG Yu-hua2，YANG Qian2，XI Te2
College Physics. 2018, 37(7): 19-22. doi:
10. 16854 /j. cnki. 1000-0712. 170648
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In both atomic physics and modern physics，the determination of atomic ground states is involved in different degrees. This is a relatively complex problem，since there are many physical principles involved. The determination of the atomic ground state is of great significance to the study of the atomic shell structure. This paper gives a theoretical basis and a simple method to determine the atomic ground state，which is used to solve the atomic state formed by electron configuration for several types of atomic ground states.
The exact solution to null geodesics at the equatorial plane in Kerr spacetime
ZHAO Fan1，HE Feng2
College Physics. 2018, 37(7): 23-24. doi:
10. 16854 /j. cnki. 1000-0712. 170603
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1466
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815
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The two first integrals of geodesics given by the Euler - Lagrange equations are found at the equatorial plane in Kerr spacetime. Combining the constraint for null geodesics，the orbit differential equation is obtained.The roots of a quartic in integrand are found and reordered. The solution of orbit differential equation can be expressed exactly by the elliptic of the first kind and the third kind.
Gravitational wave observations support the black hole area theorem
ZHAO Yun-he1，MA Yu-han2，3
College Physics. 2018, 37(7): 25-27. doi:
10. 16854 /j. cnki. 1000-0712. 170580
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1777
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490
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The black hole area theorem shows that the area of the black hole does not decrease，which corresponds to the second law of thermodynamics. We note that the four gravitational wave observations from LIGO come from the merging process of the double black hole，and thus we use these observed data to validate the area theorem. The four observations all support the black hole area theorem. In addition，we study the merge process of N black hole，and a equivalence representation of the area theorem is obtained in principle.
Discussion on the orbit property and release mechanism of the binding energy of particles outside the Schwarzschild black hole
YANG Zhi-wan
College Physics. 2018, 37(7): 28-30. doi:
10. 16854 /j. cnki. 1000-0712. 170466
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In this paper，firstly，the distribution characteristics of the equivalent potential of Schwarzschild field are analyzed，furthermore，the orbital properties of the particles under different dynamic conditions are analyzed.Finally，the mechanism of the binding energy release of bounded orbital particles is discussed.
Solid - liquid phase transition in sodium chloride aqueous solution of series concentration studied by differential scanning calorimetry
WANG Li-na1，2，DU Bin1，ZHAO Xing-yu1，2，HUANG Yi-neng1，2，ZHOU Heng-wei1
College Physics. 2018, 37(7): 31-36. doi:
10. 16854 /j. cnki. 1000-0712. 170565
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1608
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The heat flows of a series of sodium chloride aqueous solutions contained 21 molar ratios b are measured and analyzed by differential scanning calorimeter in the range of - 50 ～ 50℃. All measured solutions except water appear two endothermic peaks. The peak positions of both move to each other with the increase of b，at the same time，the intensity of high temperature peak decreases and the one of low temperature peak increases. At last，two peaks are gradually overlapped. A method to separate overlapping double peaks is proposed and the b dependent characteristic parameters of melting peak are obtained，which are consistent with the micro - phase separation model. Finally，the spatial distribution of sodium chloride aqueous solutions concentration is given. This research will provide a certain reference to deeply understand the microcosmic structure of the sodium chloride in aqueous solution and solid - liquid phase transition.
The experimental method of measuring the refractive index of transparent liquid by total reflection
Akimhazi·Malik
College Physics. 2018, 37(7): 37-39. doi:
10. 16854 /j. cnki. 1000-0712. 170161
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3983
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Refractive index is one of the important optical parameters. A new simple experimental instrument is designed by using polarized light experimental instrument ( WPZ type) stand，light source，and a diameter of 6 cm 200 ml glass beaker which of 60 × 80 × 2 ( mm3 ) rectangular transparent glass is in the middle，madding it be separated into the two parts. The refractive index of any kind of transparent liquid is measured according to the total reflection law of light. And the refractive index of distilled water，saturated sucrose and diiodomethane was measured by this method. The experimental results show that this method has the advantages of easy operation，low cost and high efficiency，and has certain reference value for the measurement of refractive index of transparent liquid.
Design and implementation of magnetic anomaly simulation system for ship wake
ZHANG Jian-sheng，ZHANG Cheng-ji，LU Xiao-lu，ZHANG Dong-quan
College Physics. 2018, 37(7): 40-46. doi:
10. 16854 /j. cnki. 1000-0712. 170475
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1317
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394
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In order to simulate quickly and accurately the magnetic anomaly caused by ship wake，the author built the mathematical model of wake magnetic anomaly based on the theory of Maxwell equation，magnetic fluid dynamics and ship hull correlation theory，and designed the simulation system for wake magnetic anomaly by using the guide tool of MATLAB software. The size and spatial distribution of wake magnetic anomalies in the course of ship motion are simulated by a designed system. We gained that the wake of magnetic anomaly in 2 - D and 3 - D space gradually wanes along the propagation direction of the distance. What’s more，the attenuation degree is related to the parameter of ship type，speed and inclination. This simulation system is easy to operate and integrates variable parameters. Besides，the simulation results are intuitive and can be repeatedly simulated，thus it is convenient for a real - time，fast and accurate simulation of wake magnetic anomalies.
Study and exploration of training optical simulation design ability and practice ability
HE Wen-sen，YANG Hua-jun，CAIYANG Wei-nan，JIANG Ping，HE Shu-hang，
College Physics. 2018, 37(7): 47-5. doi:
10. 16854 /j. cnki. 1000-0712. 170720
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1422
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390
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According to the education philosophy of emphasizing on theoretical modeling，strengthening simulation design ability，breaking through in innovative practice and promoting scientific exploration and relying on two courses，“Mathematical physical methods and simulationas”well as“Space Optical Communication Innovation Experiment”，the study and exploration of taking advantages of small - class teaching to train college students’abilities of optical simulation design and practice are carried out. Through recent teaching research and practice，a step - by - step teaching practice training mode helping college students’acquire abilities of optical simulation design is built up and exhibits prominent teaching effect on helping college students turn into innovative talents with wide range of professional knowledge，scientific exploration ability，simulation design ability and high - quality comprehensive ability.
Discussion on clamping balance problem
QIAO Ting，JIA Jian，HU Jian-hui，ZHANG Qi，HAN Zhi-jun
College Physics. 2018, 37(7): 53-56. doi:
10. 16854 /j. cnki. 1000 0712. 170700
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1346
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The problem of clamping balance is a typical issue of the multi - rigid - body balance analysis in theoretical mechanics.Based on the knowledge of static mechanics，the equilibrium conditions for clamped multiple blocks in parallel plates are discussed.The force analysis of a single block shows that the line position of the equivalent concentrated force on both sides of the block presents a ladder - like symmetry distribution. Then the critical pressure needed to maintain the balance of the system is discussed for different situation.
Theoretical and experimental research of hot water fountain
YANG Yue-ping1，ZHANG Wen-peng1，XU Hai1，ZHA Xin-pu2，
College Physics. 2018, 37(7): 57-62. doi:
10. 16854 /j. cnki. 1000-0712. 170435
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The fountain phenomena of a Mohr pipette with partially filled hot water through experiment are investigated. We design an improvement of device to avoid people throw shake Mohr pipette，forming a continuous water column，so the theoretical deduction and numerical calculation of fountains’jetting height are combined with Van der Walls equation and Bernoulli equation. We use the polynomial method to research a variety of experimental parameters and to avoid human factor due to heat transfer temperature is not easy to measure. We get the experimental results: the injection height of the hot water fountain is proportional to the temperature， the smaller the diameter of the nozzle is，the higher injection height of the hot water fountain when the absorbent amount is about 30% ～ 45% of pipette.
Focusing acoustic lens based on Fresnel zone plate
LEI Jia-yu，ZHANG Yu，HOU Chun-feng，WANG Yu-xiao
College Physics. 2018, 37(7): 63-69. doi:
10. 16854 /j. cnki. 1000-0712. 170584
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2439
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Inspired by the optical Fresnel zone plate，we improve，design and fabricate ultrasound Fresnel zone plates based on diffraction theory，make them adapt for focusing acoustic waves. The simple - structure and low - cost invention can be an ideal candidate for a series of applications in ultrasonic imaging with the advantages of great amplification and wide frequency range.
Understanding the importance of immeasurability of fundamental physical quantities via magnetic media thermodynamics
ZHANG Meng-zhi，WANG Xin，LIU Quan-hui
College Physics. 2018, 37(7): 70-72. doi:
10. 16854 /j. cnki. 1000-0712. 170607
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2508
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By analyzing the establishment of magnetic medium thermodynamics，we illustrate how physics describes the universe. Firstly，we invent some abstract concepts and establish operation rules in between. Then，we use those concepts and operation rules to bridge the known experimental results and the new experimental predictions. Some fundamental physical quantities are in general difficult to directly measure in experiments.
Measurement of gravitational acceleration via laser interferometr
HU Meng-nan，LI Hong-hui，BAI Zai-qiao
College Physics. 2018, 37(7): 73-77. doi:
10. 16854 /j. cnki. 1000-0712. 170622
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2420
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A laser interferometer to measure gravitational acceleration is built from low cost college laboratory apparatus. The device is basically a Michelson interferometer，in which the movable mirror is placed horizontally on the flat end of the plunger of an electromagnet. When the electromagnet coil is energized，the plunger will be quickly sucked back，leaving the movable mirror fall freely in air. At the stage of falling，the interference light intensity is recorded by an oscilloscope，and by fitting the signal with local sine waves，position of the movable mirror can be obtained at a precision much higher than the half wavelength of the laser. Finally，gravitational acceleration is extracted from the displacement - time curve of the movable mirror by a quadratic fitting. By using the data of 10 ms falling，which corresponds to displacement about 0. 5 mm，repeatable result of the gravitational acceleration in Beijing is obtained as 9. 803 ± 0. 003 m /s2 .
The NMR measuring of oil and moisture content of oil seeds based on the CPMG sequence
MA Yan-ning，QIAN Jian-qiang，HUI Zhao-yang，DU Yun-yi，CHEN Meng-shi
College Physics. 2018, 37(7): 78-81. doi:
10. 16854 /j. cnki. 1000-0712. 170518
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1609
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The oil and moisture content is an important standard to measure the quality of oil seeds. Nuclear magnetic resonance ( NMR) ，as a new measurement，is more valued. Unknown oil and moisture content and using low field NMR experimental instrument，we put forward a new CPMG sequence measuring method. By using this method，it also measures the oil and moisture content of oil seeds. This paper expands and inspires NMR students’ experiments. And students would have a more profound understanding for the application of nuclear magnetic resonance
Just Accepted
