If a plane monochromatic electromagnetic wave is incident on a free particle with charge and mass , then the particle experiences acceleration and, therefore, radiates. The direction of radiation does not coincide with the direction of the incident wave, while its frequency during nonrelativistic motion coincides with the frequency of the incident field. On the whole, this effect can be considered as scattering of the incident radiation.
The instantaneous value of the radiation power for a particle with a charge in non-relativistic motion is determined by the Larmor formula (14.21):
where is the angle between the direction of observation and the acceleration. The acceleration is due to the action of the falling plane electromagnetic wave. Denoting the wave vector as k, and the polarization vector as
through , we write the electric field of the wave in the form
According to the non-relativistic equation of motion, the acceleration is
(14.99)
If we assume that the charge displacement over the period of oscillation is much less than the wavelength, then the time-averaged square of acceleration will be equal to. In this case, the average power radiated per unit solid angle is equal to
Since the described phenomenon is most simply considered as scattering, it is convenient to introduce the effective differential scattering cross section, defining it as follows:
The energy flux of the incident wave is determined by the time-averaged value of the Poynting vector for plane wave, i.e. equal to . Thus, according to (14.100), for the differential effective cross section, scattering, we obtain
If the incident wave propagates in the direction of the axis and the polarization vector makes an angle with the axis as shown in Fig. 14.12, then the angular distribution is determined by the factor
For unpolarized incident radiation, the differential scattering is obtained by averaging over the angle , which leads to the relation
This is the so-called Thomson formula for the scattering of incident radiation by a free charge. She describes the scattering x-rays on electrons or y-rays on protons. Angular
the radiation distribution is shown in Fig. 14.13 (solid curve). For the total effective scattering cross section, the so-called Thomson scattering cross section, we obtain
For electrons. The quantity cm, which has the dimension of length, is usually called the classical radius of the electron, since a uniform charge distribution equal to the charge of the electron must have a radius of such an order that its own electrostatic energy is equal to the rest mass of the electron (see Chap. 17).
Thomson's classical result is valid only at low frequencies. If the frequency ω becomes comparable with the value , i.e., if the photon energy is comparable to or exceeds the rest energy, then quantum-mechanical effects begin to significantly affect. Another interpretation of this criterion is also possible: quantum effects can be expected when the radiation wavelength becomes comparable to or less than the Compton wavelength of the particle. At high frequencies, the angular distribution of radiation is more concentrated in the direction of the incident wave, as shown by the dotted curves in Fig. 14.13; in this case, however, the radiation cross section for the zero angle always coincides with that determined by the Thomson formula.
The total scattering cross section turns out to be smaller than the Thomson scattering cross section (14.105). This is the so-called Compton scattering. For electrons, it is described by the Klein-Nishina formula. Here we give for reference the asymptotic expressions
total scattering cross section, determined by the Klein-Nishina formula.
[according to English. physicist W. Thomson (W. Thomson; 1824 - 1907)] - a formula expressing the dependence of the period T of undamped natural vibrations in oscillatory circuit on its parameters - inductance L and capacitance C: T = 2PI root of LC (here L in H, C in F, G in s).
- - the release or absorption of heat in a current-carrying conductor, along which there is a temperature gradient, which occurs in addition to the release of Joule heat. Thomson heat Qs is proportional to...
Physical Encyclopedia
- - throttle effect, - change in gas temperature during its adiabatic. throttling, i.e., lowering the gas pressure as it flows through a porous partition, diaphragm or valve without heat exchange with the environment ...
- - the potential difference that forms between two points of a metal conductor if these two points have different temperatures. The effect is named for William Thomson. see also THERMOELECTRICITY...
Scientific and technical encyclopedic dictionary
- - see Throttling...
Natural science. encyclopedic Dictionary
- - see Glycogenosis VII...
Big Medical Dictionary
- - a tool for crushing stones in the bladder with a working part in the form of metal sponges, which were brought together with a screw; forerunner of modern mechanical lithotripters...
Big Medical Dictionary
- - see Poikiloderma hereditary sclerosing ...
Big Medical Dictionary
- - a formula that looks like: where a1, A2,..., An are incompatible events, General scheme F.'s applications in. g.: if event B can occur in decomp. conditions under which n hypotheses A1, A2, .....
Geological Encyclopedia
- - the release or absorption of heat, in addition to Joule, in a current-carrying conductor, in which there is a temperature difference. The effect is described by f-loy: O = t / t Delta T, where I - current strength, t - time, Delta T - temperature difference. t - coefficient ...
Big encyclopedic polytechnic dictionary
- - 1...
Encyclopedic Dictionary of Metallurgy
- - change in gas temperature as a result of its slow flow under the action of a constant pressure drop through the throttle - local obstruction to the gas flow ...
- - "Thomson Organization, Limited", one of the largest newspaper and publishing associations in the UK. At the head of the concern is Baron G. Thomson ...
Great Soviet Encyclopedia
- - an underwater ridge between the Faroe Islands and the northern coast of the island of Great Britain ...
Great Soviet Encyclopedia
- - I Thomson thermoelectric effect, one of the thermoelectric phenomena...
Great Soviet Encyclopedia
- - an underwater ridge separating the depression of the Atlantic approx. from the depression of the Norwegian m., prevents deep water exchange between them. Length approx. 100 km...
- - additional release or absorption of heat during the passage of current through a conductor in which there is a temperature difference. The amount of heat is proportional to the current and temperature difference...
Big encyclopedic dictionary
"THOMSON FORMULA" in books
MAXWELL'S METHOD AND THOMSON'S "ANALOGIES"
From Maxwell's book author Kartsev Vladimir PetrovichMAXWELL'S METHOD AND THOMSON'S "ANALOGY" It was clear to Maxwell that Faraday was right and his lines of force were a truly great discovery. But the Faraday field lines were not suitable for calculations. It was impossible, for example, to say in advance what the lines of force of the two sets
Its formula
From the book The wrong side of the screen the author Maryagin LeonidHis formula Shortly before his death, Dovzhenko dreamed of leaving Mosfilm and forming his own studio. I, young, in love with the Mosfilm giant, was dumbfounded. - Why do you not like Mosfilm? I asked Alexander Petrovich timidly. And I received a significant answer:
Formula
From the book Reflections on Personal Development author Adizes Itzhak CalderonFormula In my understanding, the formula, ruling the world, is nothing but absolute, pure love (or, in other words, complete integration). And integration is a function of mutual respect and trust. So where was God during the Holocaust? The formula explains what happened:
Formula
From the book Get rid of bad debts author Kiyosaki Robert ToruThe Formula You've completed the first four steps and are now ready to move on to the bad debt elimination formula. Steps 5 to 10 will lead you to the specific formula that Robert and I used to get rid of all the debt that was hanging on us.
From a foreword by former British intelligence chief Basil Thomson
From the book American Intelligence During the World War author Johnson Thomas MFrom a foreword by former British intelligence chief Basil Thomson If I undertake to write a preface to this book, I do it because I personally knew many of Johnson's colleagues and I can appreciate the diligence with which they carried out their work. The author says
Chapter 9. 1840 - 1859 Cooke-Wheatstone, Morse, Siemens telegraphs, Alliance machine, Thomson formula, Hughes telegraph, Plante accumulator
the author Kuchin VladimirChapter 9. 1840 - 1859 Cooke-Wheatstone, Morse, Siemens telegraphs, Alliance machine, Thomson formula, Hughes telegraph, Plante accumulator 1840 Cooke and Wheatstone telegraph, Morse telegraph In 1840, January 21, the British Cook and Wheatstone patent in England 5-hand telegraph (BP 8345),
1853 Siemens, Halske, Fizeau, Thomson formula
From the book Popular History - From Electricity to Television the author Kuchin Vladimir1853 Siemens, Halske, Fizeau, Thomson's formula In 1853, Ernst Werner von Siemens began the construction of a telegraph line of his own design in Russia from St. Petersburg to Sevastopol, the work was completed in 1856. In Russia at that time there was Crimean War, and generous funding
Joule - Thomson effect
From the book Great Soviet Encyclopedia (J) of the author TSBThe Thomson Committee On April 10, 1940, members of the Thomson Committee met in the old Victorian building of the Royal Society in London. This government-subsidized body was established to deal with the military applications of atomic energy. Gentlemen! - Foreword by Garner Thomson
From the book TRANSFORMATION by Richard Bandler
Foreword by Garner Thomson I was deeply honored when I was asked to edit Dr. Richard Bandler's book on hypnosis and neurolinguistic programming. Life does not often bring us together with such people who make the impossible possible for the sake of good.
The formula of the path is the formula of life
From the book Life is a game. Rules of the winners author Zyuzginov AlexanderThe formula of the path is the formula of life Life is a journey to the most unknown corner in the whole world - Yourself. Nobody knows their limits. And I'm pretty sure there aren't any. I don’t know what I will take with me on the road, what I will refuse, what I will not notice, what I will cry, laugh, regret about. I
Lesson type: a lesson of initial acquaintance with the material and practical application knowledge and skills.
Lesson duration: 45 minutes.
Goals:
Didactic – generalize and systematize knowledge about the physical processes occurring in an electromagnetic oscillatory circuit
create conditions for the assimilation of new material, using active teaching methods
educational I– to show the universal nature of the theory of oscillations;
Educational – develop the cognitive processes of students, based on the application scientific method knowledge: similarity and modeling; forecasting the situation; to develop in schoolchildren methods of effective processing educational information, continue the formation of communicative competencies.
Educational – to continue the formation of ideas about the relationship between natural phenomena and a single physical picture of the world
Lesson objectives:
1. Educational
ü formulate the dependence of the period of the oscillatory circuit on its characteristics: capacitance and inductance
ü to study the techniques for solving typical problems on the "oscillatory circuit"
2. Educational
ü continue the formation of skills to compare phenomena, draw conclusions and generalizations based on experiment
ü work on the formation of skills to analyze properties and phenomena based on knowledge.
3. Nurturers
ü to show the significance of experimental facts and experiment in human life.
ü reveal the significance of the accumulation of facts and their clarifications in the cognition of phenomena.
ü to acquaint students with the relationship and conditionality of the phenomena of the surrounding world.
TCO:computer, projector, IAD
Preliminary preparation:
- individual evaluation sheets - 24 pieces
- route sheets (colored) - 4 pieces
Technological map of the lesson:
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Lesson stages |
Active Methods |
ICT support |
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1.Organizational |
Epigraph of the lesson |
Slide №1,2 |
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2. Knowledge update (generalization of previously studied material - testing knowledge of formulas on the topic “Mechanical and electromagnetic oscillations”) |
Get the error! Formulas are given with errors. Assignment: correct mistakes, then peer-check, scoring |
Slide #3 Slide #4 slide number 5 |
|
3.Activity motivation : why this topic is studied in the 11th grade physics course (the word of the teacher-thesis) The oscillatory circuit is the main part of the radio receiver. The purpose of the receiver is to receive oscillations (waves) of various frequencies. The simplest oscillatory circuit is a coil and a capacitor with characteristics of inductance and capacitance, respectively. How does the receiving capacity of the circuit depend on the coil and the capacitor? |
Keywords CMD (collective mental activity) The groups have 5 minutes to by brainstorming give a general interpretation of these terms and suggest how they will appear in the next lesson.
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slide number 6 |
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4. Goal setting Find out the dependence of the period of the electromagnetic oscillatory circuit on the capacitance of the capacitor and the inductance of the coil. Learn how to use formulas to solve problems. |
(the goal is set by the students themselves, using key terms)
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|
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5. Formation of new knowledge
(using the experience of students when learning new material) What period formula do you already know? T=2π/ω; ω =2πν What formula for cyclic frequency was obtained in the last lesson? Connect these two formulas and get the formula that the king of Victorian physics, William Thomson, derived: History of Lord Thomson |
Virtual laboratory (video experiment)
Virtual laboratory (interactive model)
"Thick" questions: Explain why...? Why do you think...? What is the difference …? Guess what happens if...? "Subtle" questions: What? Where? How? Can...? Will it …? Do you agree …? Basket - method (analysis of the practical situation in groups) |
Slide #9 Slide #10 Slide №11,12 |
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6. Control of acquired knowledge Debrief one problem on the board In groups, come up with a condition for a qualitative or calculation problem, write it down on the route sheet, the next group solves this problem, the speaker shows on the board
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Thomson formula:
The period of electromagnetic oscillations in an ideal oscillatory circuit (i.e., in such a circuit where there is no energy loss) depends on the inductance of the coil and the capacitance of the capacitor and is found according to the formula first obtained in 1853 by the English scientist William Thomson:
The frequency is related to the period by an inversely proportional dependence ν = 1/Т.
For practical applications, it is important to obtain undamped electromagnetic oscillations, and for this it is necessary to replenish the oscillatory circuit with electricity in order to compensate for the losses.
To obtain undamped electromagnetic oscillations, a undamped oscillation generator is used, which is an example of a self-oscillating system.
See below "Forced Electrical Vibrations"
FREE ELECTROMAGNETIC OSCILLATIONS IN THE CIRCUIT
ENERGY CONVERSION IN AN OSCILLATING CIRCUIT
See above "Oscillation circuit"
NATURAL FREQUENCY IN THE LOOP
See above "Oscillation circuit"
FORCED ELECTRICAL OSCILLATIONS
ADD DIAGRAM EXAMPLES
If in a circuit that includes inductance L and capacitance C, the capacitor is somehow charged (for example, by briefly connecting a power source), then periodic damped oscillations will occur in it:
u = Umax sin(ω0t + φ) e-αt
ω0 = (Natural oscillation frequency of the circuit)
To ensure undamped oscillations, the generator must necessarily include an element capable of connecting the circuit to the power source in time - a key or an amplifier.
In order for this key or amplifier to open only at the right time, it is necessary Feedback from the circuit to the control input of the amplifier.
An LC-type sinusoidal voltage generator must have three main components:
resonant circuit
Amplifier or key (on a vacuum tube, transistor or other element)
Feedback
Consider the operation of such a generator.
If the capacitor C is charged and it is recharged through the inductance L in such a way that the current in the circuit flows counterclockwise, then e occurs in the winding that has an inductive connection with the circuit. d.s., blocking the transistor T. The circuit is disconnected from the power source.
In the next half-cycle, when the reverse charge of the capacitor occurs, an emf is induced in the coupling winding. of another sign and the transistor opens slightly, the current from the power source passes into the circuit, recharging the capacitor.
If the amount of energy supplied to the circuit is less than the losses in it, the process will begin to decay, although more slowly than in the absence of an amplifier.
With the same replenishment and energy consumption, the oscillations are undamped, and if the replenishment of the circuit exceeds the losses in it, then the oscillations become divergent.
The following method is usually used to create a undamped character of oscillations: at small amplitudes of oscillations in the circuit, such a collector current of the transistor is provided in which the replenishment of energy exceeds its consumption. As a result, the oscillation amplitudes increase and the collector current reaches the saturation current value. A further increase in the base current does not lead to an increase in the collector current, and therefore the increase in the oscillation amplitude stops.
AC ELECTRIC CURRENT
AC GENERATOR (ac.11 class. p.131)
EMF of a frame rotating in the field
Alternator.
In a conductor moving in a constant magnetic field, an electric field is generated, an EMF of induction occurs.
The main element of the generator is a frame rotating in a magnetic field by an external mechanical motor.
Let us find the EMF induced in a frame of size a x b, rotating with an angular frequency ω in a magnetic field with induction B.
Let in the initial position the angle α between the magnetic induction vector B and the frame area vector S zero. In this position, no charge separation occurs.
In the right half of the frame, the velocity vector is co-directed to the induction vector, and in the left half it is opposite to it. Therefore, the Lorentz force acting on the charges in the frame is zero
When the frame is rotated through an angle of 90o, the charges are separated in the sides of the frame under the action of the Lorentz force. In the sides of the frame 1 and 3, the same induction emf arises:
εi1 = εi3 = υBb
The separation of charges in sides 2 and 4 is insignificant, and therefore the induction emf arising in them can be neglected.
Taking into account the fact that υ = ω a/2, the total EMF induced in the frame:
εi = 2 εi1 = ωB∆S
The EMF induced in the frame can be found from Faraday's law of electromagnetic induction. The magnetic flux through the area of the rotating frame changes with time depending on the angle of rotation φ = wt between the lines of magnetic induction and the area vector.
When the loop rotates with a frequency n, the angle j changes according to the law j = 2πnt, and the expression for the flow takes the form:
Φ = BDS cos(wt) = BDS cos(2πnt)
According to Faraday's law, changes in the magnetic flux create an induction emf equal to minus the rate of flux change:
εi = - dΦ/dt = -Φ’ = BSω sin(ωt) = εmax sin(wt) .
where εmax = wBDS is the maximum EMF induced in the frame
Therefore, the change in the EMF of induction will occur according to a harmonic law.
If, with the help of slip rings and brushes sliding along them, we connect the ends of the coil with an electrical circuit, then under the action of the induction EMF, which changes over time according to a harmonic law, forced electrical oscillations of the current strength - alternating current - will occur in the electrical circuit.
In practice, a sinusoidal EMF is excited not by rotating a coil in a magnetic field, but by rotating a magnet or electromagnet (rotor) inside the stator - stationary windings wound on steel cores.
Go to page:
Lesson No. 48-169 Oscillatory circuit. Free electromagnetic oscillations. Energy conversion in an oscillatory circuit. Thompson formula.
fluctuations- movements or states that repeat in time.Electromagnetic vibrations -These are vibrations of electrical andmagnetic fields that resistdriven by periodic changecharge, current and voltage. An oscillatory circuit is a system consisting of an inductor and a capacitor(Fig. a). If the capacitor is charged and closed to the coil, then current will flow through the coil (Fig. b). When the capacitor is discharged, the current in the circuit will not stop due to self-induction in the coil. The induction current, in accordance with the Lenz rule, will flow in the same direction and recharge the capacitor (Fig. c). The current in this direction will stop, and the process will repeat in the opposite direction (Fig. G).In this way, in hesitationcircuitdyat electromagnetic oscillationsdue to the conversion of energyelectric field condensatera(
W e =
)
into the energy of the magnetic field of the coil with current(W M = 
),
and vice versa. Harmonic oscillations - periodic changes physical quantity depending on time, occurring according to the law of sine or cosine.
q "= - ω 0 2 q (q" is the second derivative.
The main characteristics of the oscillatory motion:
The oscillation period is the minimum period of time T, after which the process is completely repeated.
Amplitude of harmonic oscillations - module the greatest value fluctuating amount.
Knowing the period, you can determine the frequency of oscillations, that is, the number of oscillations per unit of time, for example, per second. If one oscillation occurs in time T, then the number of oscillations in 1 s ν is determined as follows: ν = 1/T.
Recall that in the International System of Units (SI), the oscillation frequency is equal to one if one oscillation occurs in 1 s. The unit of frequency is called the hertz (abbreviated as Hz) after the German physicist Heinrich Hertz.
After a period of time equal to the period T, i.e., as the cosine argument increases by ω 0
T, the value of the charge is repeated and the cosine takes the same value. From the course of mathematics it is known that the smallest period of the cosine is 2n. Therefore, ω 0
T=2π, whence ω 0
= 
=2πν Thus, the quantity ω 0
- this is the number of oscillations, but not for 1 s, but for 2n s. It is called cyclical or circular frequency.
Frequency free vibrations called natural frequency of the vibrationalsystems. Often in what follows, for brevity, we will refer to the cyclic frequency simply as the frequency. Distinguish the cyclic frequency ω 0 on the frequency ν is possible by notation.
By analogy with the solution differential equation for a mechanical oscillatory system cyclic frequency of free electricfluctuations is: ω 0 = 
The period of free oscillations in the circuit is equal to: T= 
=2π 
- Thomson formula.
Oscillation phase (from Greek word phasis - appearance, stage of development of a phenomenon) - the value of φ, which is under the sign of cosine or sine. The phase is expressed in angular units - radians. The phase determines the state of the oscillatory system at a given amplitude at any time.
Oscillations with the same amplitudes and frequencies may differ from each other in phases.
Since ω 0
= , then φ= ω 0
T=2π
. The ratio shows what part of the period has passed from the moment the oscillations began. Any value of time expressed in fractions of a period corresponds to a phase value expressed in radians. So, after time t= 
(quarter period) φ= 
, after half the period φ \u003d π, after the whole period φ \u003d 2π, etc. You can plot the dependence
different phase values φ.
Correspondence between mechanical and electrical quantities in oscillatory processes
Mechanical quantities
Tasks.942(932). The initial charge reported to the capacitor of the oscillatory circuit was reduced by 2 times. How many times have changed: a) voltage amplitude; b) current amplitude;
c) the total energy of the electric field of the capacitor and magnetic field coils?
943(933). With an increase in the voltage on the capacitor of the oscillatory circuit by 20 V, the amplitude of the current strength increased by 2 times. Find the initial stress.
945(935). The oscillatory circuit consists of a capacitor with a capacity of C = 400 pF and an inductance coil
L = 10 mH. Find the amplitude of current oscillations I t , if the amplitude of voltage fluctuations U t = 500 V.952(942). After what time (in fractions of the period
t / T) on the capacitor of the oscillatory circuit for the first time will there be a charge equal to half the amplitude value?957(947). What inductance coil should be included in the oscillatory circuit in order to obtain a free oscillation frequency of 10 MHz with a capacitor capacitance of 50 pF?
Oscillatory circuit. The period of free oscillations.
1. After the capacitor of the oscillatory circuit was charged
q \u003d 10 -5 C, damped oscillations appeared in the circuit. How much heat will be released in the circuit by the time the oscillations in it are completely damped? Capacitor capacitance C \u003d 0.01 μF.2. The oscillatory circuit consists of a 400nF capacitor and a 9µH inductor. What is the natural oscillation period of the circuit?
3. What inductance should be included in the oscillatory circuit in order to obtain a natural oscillation period of 2∙ 10 -6 s with a capacitance of 100pF.
4. Compare spring rates
k1/k2 of two pendulums with weights of 200g and 400g, respectively, if the periods of their oscillations are equal.5. Under the action of a motionlessly hanging load on the spring, its elongation was 6.4 cm. Then the load was pulled and released, as a result of which it began to oscillate. Determine the period of these oscillations.
6. A load was suspended from the spring, it was taken out of equilibrium and released. The load began to oscillate with a period of 0.5 s. Determine the elongation of the spring after the oscillation stops. The mass of the spring is ignored.
7. For the same time, one mathematical pendulum makes 25 oscillations, and the other 15. Find their lengths if one of them is 10 cm shorter than the other.8. The oscillatory circuit consists of a 10mF capacitor and a 100mH inductor. Find the amplitude of voltage fluctuations if the amplitude of current fluctuations is 0.1A9. The inductance of the coil of the oscillatory circuit is 0.5mH. It is required to tune this circuit to a frequency of 1 MHz. What should be the capacitance of the capacitor in this circuit?Exam questions:
1. Which of the following expressions determines the period of free oscillations in an oscillatory circuit? BUT.; B. 
; AT. 
; G. 
; D. 2.
2
. Which of the following expressions determines the cyclic frequency of free vibrations in an oscillatory circuit? A. B. 
AT. 
G. 
D. 2π
3. The figure shows a graph of the dependence of the X coordinate of a body performing harmonic oscillations along the x axis on time. What is the period of oscillation of the body?
A. 1 s; B. 2 s; B. 3 s . D. 4 p.
4. The figure shows the wave profile at a certain point in time. What is its length?
A. 0.1 m. B. 0.2 m. C. 2 m. D. 4 m. D. 5 m.5
. The figure shows a graph of the dependence of the current through the coil of the oscillatory circuit on time. What is the period of current oscillation? A. 0.4 s. B. 0.3 s. B. 0.2 s. D. 0.1 s. E. Among the answers A-D, there is no correct one.
6. The figure shows the wave profile at a certain point in time. What is its length?
A. 0.2 m. B. 0.4 m. C. 4 m. D. 8 m. D. 12 m.
7. Electric oscillations in the oscillatory circuit are given by the equation q \u003d 10 -2 ∙ cos 20t (C).
What is the amplitude of charge oscillations?
BUT . 10 -2 Cl. B.cos 20t Cl. B.20t Cl. D.20 Cl. E. Among the answers A-D, there is no correct one.
8. When harmonic vibrations along the OX axis, the coordinate of the body changes according to the law X=0.2cos(5t+ 
). What is the amplitude of the body's vibrations?
A. Xm; B. 0.2 m; C. cos(5t+) m; (5t+)m; D.m
9. Oscillation frequency of the wave source 0.2 s -1 wave propagation speed 10 m/s. What is the wavelength? A. 0.02 m. B. 2 m. C. 50 m.
D. According to the condition of the problem, it is impossible to determine the wavelength. E. Among the answers A-D, there is no correct one.
10. Wavelength 40 m, propagation speed 20 m/s. What is the oscillation frequency of the wave source?
A. 0.5 s -1 . B. 2 s -1 . V. 800 s -1 .
D. According to the condition of the problem, it is impossible to determine the oscillation frequency of the wave source.
E. Among the answers A-D, there is no correct one.
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