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Файл:Basics of Physics II (Основы физики II). Учебное пособие
.pdf
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SPEAKING
14. Extended discussion questions:
1) Why has light been such an interesting phenomenon of the research for many decades and centuries?
2) What is the red shift? What theories were based on the features of it?
3) What is luminiferous aether? Does it exist?
15. In pairs, role-play the conversation between: a) an optics professor and his student; b)
two groupmates one of whom missed the last lecture. Explain to your partner the properties
of light. The asking student must prepare 2-3 questions before you start.
16. Challenge questions — test yourself!
a) What is the relationship between the speed of light, wavelength, and frequency of electromagnetic radiation?
b) What are the properties of electromagnetic waves?
c) What properties of light allow shadows to form?
d) Why is visible light useful in photosynthesis, while other forms of electromagnetic radiation are
not?
e) How was the speed of light calculated?
f) If a light wave has a long wavelength, is it likely to have a low or high frequency?
g) What is Doppler’s effect?
h) Which has a higher frequency: red light or green light?
i) Why do fluorescent dyes emit a different color of light than they absorb?
j) Why can't ultraviolet light pass through glass?
k) What is the speed of a photon in water?
LISTENING
17. You are going to watch a video named What is light? Before you start, read the next words
from this video and make sure you understand their meanings:
in a nutshell, quantity, to put smth into perspective, from one’s standpoint, coincidence, to alter
18. Watch the video and answer the questions below:
1) What is light?
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2) What are properties of a photon?
3) What is called electromagnetic spectrum?
4) What information is given about gamma rays and radio waves?
5) What makes visible light special?
6) Why is light said to be helpful for survival?
7) How does light appear?
8) What is the speed of light (in vacuum)?
19. What physical theories and questions were mentioned at the end of the video? Do you
know anything about them? What other theories and problems are connected with light?
GRAPH DESCRIPTION
20. Describe the graph showing the light spectrum
DEVICE EXPLANATION
21. Using the facts below and the scheme of the device, explain the work of the spectrometer:
✓ its structure;
✓ its purpose;
✓ how do you use it.
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About the device
A spectrophotometer is a device used to measure light at a specific
wavelength. It consists of two parts: a spectrometer and a photometer.
The spectrometer provides light at a specific wavelength. The photometer measures how intense the light is. By calculating the amount of
light that a solution is able to absorb and applying Beer's Law, the
spectrophotometer can determine the concentration of a colored solution.
Working mechanism
A ray of light enters a spectrometer, through a collimator slit (which
converts the incoming light into a parallel beam) and falls on the diffraction grating. These gratings are surfaces with several thousand
lines etched into them, which cause the light to get diffracted. The
readable side of a DVD or a compact disc, for example, acts as a diffraction grating, splitting incident visible light, into its fundamental
wavelength components.
Tips
• Special light filters may be required on some spectrophotometers
if working at certain wavelengths.
• The machine must be zeroed out after each sample or if changing
the wavelength.
Warning
• Failure to allow the spectrophotometer enough time to warm can
result in erroneous results.
• Make sure cuvettes are free of any particles, smudges or finger-
prints, as these can throw the machine’s calculations off.
• Spectrophotometers are expensive machines. Take care to not in-
advertently damage the machine while using it.
TRANSLATION
22. Translate from English into Russian:
The electromagnetic spectrum describes light as a wave which has a particular wavelength. The
description of light as a wave first gained acceptance in the early 1800's when experiments by Thomas
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Young, François Arago, and Augustin Jean Fresnel showed interference effects in light beams, indicating that light is made of waves. By the late 1860's light was viewed as part of the electromagnetic
spectrum. However, in the late 1800's a problem with the wave-based view of light became apparent
when experiments measuring the spectrum of wavelengths from heated objects could not be explained
using the wave-based equations of light. This discrepancy was resolved by the works of 1 in 1900,
and 2 in 1905. Planck proposed that the total energy of light is made up of indistinguishable energy
elements, or a quanta of energy. Einstein, while examining the photoelectric effect (the release of
electrons from certain metals and semiconductors when struck by light), correctly distinguished the
values of these quantum energy elements. For their work in this area Planck and Einstein won the
Nobel prize for physics in 1918 and 1921, respectively and based on this work, light may be viewed
as consisting of "packets" or particles of energy, called photons.
23. Translate from Russian into English:
Долгое время физики полагали, что им не удастся осуществить преломление гамма-лучей. Франко-германская группа учёных сумела экспериментально доказать, что это возможно.
Для этого они использовали особую кремниевую линзу.
Чтобы понять, в чём состоит "невозможность" преломления гамма-излучения, необходимо вспомнить школьные уроки физики. Так, известно, что, проходя через различные среды,
волны электромагнитного излучения (к ним, в частности, относятся свет и гамма-лучи) способны изменять траекторию распространения. Степень такого отклонения измеряется коэффициентом преломления и определяется соотношением фазовых скоростей электромагнитных
волн в вакууме и в среде. Если скорости равны, то коэффициент равен единице (то есть преломление отсутствует). К примеру, видимый свет, распространяясь в воздушной среде при
обычных условиях, имеет коэффициент преломления, практически равный единице.
Свойства электромагнитных волн видимого диапазона позволяют относительно свободно им управлять (отражать, фокусировать и рассеивать). Более того, недавно физики
научились изгибать лучи света под любым углом без внешнего воздействия.
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PART 2
Models of Light
“It seems as though we must use sometimes the one theory and sometimes the other, while at times
we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of
reality; separately neither of them fully explains the phenomena of light, but together they do.”
Albert Einstein
LEAD-IN
1. Answer the questions:
1) What is a particle?
2) What is a wave?
3) Is light a particle or a wave?
PRE-READING
2. Write derivatives of the following words:
E.g. theory — theories, theoretical, theoretically, to theorize, theorist
magnet
light
wave
locus
READING
3. Restore the order of sentences in paragraph 2 (Classical Particles).
4. Read the whole text and then insert the words at the end of this text into spaces (a — m):
The Problem Posed by Light
Overview
In classical physics, especially mechanics and electricity and magnetism, two (a)________ and
very useful concepts have been invented and used repeatedly, that of particles and that of waves.
However, to explain phenomena on the atomic level of size, the distinction between waves and particles becomes (b)________, and an important modification, involving probability, must be made.
Because the separate concepts of particle and of wave are so natural and satisfying for phenomena on
the human scale it is somewhat difficult to explain why and how they must be modified and combined
in order to describe the behavior of very small objects. Our most complete theory of light is a “quan-
tum field” theory having both wavelike and particle-like properties that is, incorporating “wave-
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particle dualism.” We will (c)________ the relationships between classical particles, classical elec-
tromagnetic waves and quantum field theory by asking what each of them predicts for a single
(d)________ experiment.
Classical Particles
1___ For example, in Fig. 1 we have a particle with
charge q moving near a charged plate. 2___ The subsequent motion of the particle in the next infinitesimal
interval of time is governed by: 𝑎 = 𝐹/𝑚 = (𝑞/𝑚)𝐸.
3___ A particle is characterized by having infinitesimal
size and a definite location in space at each instant of
time. 4 ___ At each instant of time, the particle experi-
ences a force 𝐹= 𝑞𝐸 determined by the electric field
at the location of the particle. 5___ If there are no forces
acting on it, the particle travels in a straight line at constant speed. 6___ It may have mass and an electrical
charge, it certainly has momentum and carries kinetic
energy. 7___ As time increases, the particle moves
along a definite trajectory, which is determined entirely
by local conditions at the point where the particle is.
Classical Waves
The “wave” concept is abstracted from many different phenomena that are only geometrically
similar, such as waves on the surface of water, sound in gas, liquid or solid, electromagnetic waves,
displacement of a (e)________ string or a stretched membrane (drumhead, flapping sail) etc. In each
case there is some “field” quantity varying smoothly in 1, 2 or 3 dimensions. (For water waves,
vibrating strings and membranes it is the displacement of particles from their equilibrium position;
for sound in air it can be density or pressure variations; for electromagnetic waves there are six var-
ying fields, the three components of 𝐸 and the three components of 𝐵.)
We will not need to consider the detailed electromagnetic wave picture for light that can be
(f)________from Maxwell's differential equations of the electromagnetic field, and which correctly
predicts the light's velocity, its polarization (i.e., the fact that the 𝐸 vector is perpendicular to the
direction of propagation of the light wave) and the wave's behavior at surface boundaries with conducting and dielectric materials. Rather, we will consider the most characteristic property of any wave,
that it undergoes diffraction at an obstacle.
The momentum and energy carried by a wave are not concentrated at a point, but are spread out
smoothly over a (g)________ volume. This is in contrast to the very small sizes of atomic particles,
and this contrast is what makes it hard to imagine an entity which is (h)________ a “wave” and a
“particle.” In fact, we will see that light is composed neither of classical waves nor of classical parti-
cles, but is a new kind of entity that behaves in certain ways like a particle and in other ways like a
wave. A (i)________ description ties these aspects together.
The Nature of Light
Is light:
— A wave?
Evidence: diffraction and interference experiments.
Figure 1. Local influences on the trajectory of a
charged particle near a charged plate.
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— An electromagnetic
wave?
Evidence: Maxwell's equations predict such behavior as its speed in
vacuum, Snell's law of refraction, polarization, generation of long
waves by simple electromagnetic circuits, etc.
— A particle?
Evidence: Compton effect, photoelectric effect, photochemical reactions, etc.
The (j)________ contradictory wave and particle natures of light are (k)________ by quantum
field theory. Its basic statement is: “The intensity (at a given point in space and time) of an electromagnetic wave of frequency ν gives the probability, and only the probability, that energy in the
amount hν may be transferred between the wave and an external object at that point in space.” The
wave, particle and quantum field theory ideas can be contrasted, compared and explained by using
each to predict the results of a Fraunhfer single slit diffraction experiment.
[…]
Light Is Not Particles, Not Waves
Light cannot be categorized as either classical particles or classical waves. If it were
(l)________ as a classical particle it would not produce a diffraction pattern, but light diffracts. If it
were a classical wave, its energy and momentum would have a continuous distribution in space and
time, but light often acts as if it consists of localized photons having discrete energy and momenta.
Thus light cannot be said to be (m)________ one or the other.
seemingly
simultaneously
taut
distinct
reconciled
clarify
blurred
slit
classifiable
probabilistic
derived
finite
intrinsically
POST-READING
VOCABULARY
5. Find words in the text (in bold) which fit the following definitions:
1) an extremely short period of time;
2) removed or separated (from smth);
3) very hard or firm;
4) unable for both to be either true or false under the same circumstances;
5) the state of being different;
6) spreading or supplying smth;
7) a flat piece of metal, especially on machinery or a building;
8) including;
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9) in approximately equal amounts;
10) the removal of something from its usual place or position by something which then occupies
that place or position;
11) make a declaration about smth in advance.
6. In pairs or small groups define the following words (do not forget to use terms!)
equilibrium, boundary, wave, entity, propagation, drumhead, evidence, polarization, refraction, generation, circuit
7. Fill in the gaps:
Part A
equilibrium distinction propagation boundaries distribution evidence generation circuit
refraction string
1) Latest studies of cosmic background radiation showed the ___________ of light wasn’t smooth;
there were brighter and darker spots on the map.
2) According to Newton, rectilinear ___________ of light is possible because photons are unaffected
by gravity, hence they travel in a straight line from its source at high speed.
3) A(n) ___________ of the existence of other universes is unlikely to be found in the near future.
4) In a chemical reaction, chemical ___________ is the state in which the concentrations of the reactants and products have not yet changed with time.
5) Referring to Figure 1, consider a taut ___________ stretched between two fixed points at x = 0
and x = L.
6) ___________ of degree seemed to be the main factor of getting this result. In the last experiment
a bigger amount of sodium was used.
7) Only twenty years ago the Frenchman Laussedat noted a(n) ___________ of the solar disc during
an eclipse.
8) Scientists still cannot state what exactly is located at the ___________ of the Solar system, thus
the interest in this research is high enough to get more funding.
9) My attempts to cut through the cabling will break the electrical ___________.
10) We have greatly expanded our gas production and power ___________ activities through acquisitions and investment.
Part B
smoothly incorporating entirely subsequent simultaneously contradictory classifiable
predicting reconcile displaced
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1) First results of my research are promising but only the ___________ study will show the worth of
the whole theory.
2) His line of work was to check from time to time if the engine is working ___________. When it
didn’t, he stopped the whole mechanism and oiled its parts.
3) Two levers are located in opposite sides of the control room and must be pushed ___________, so
that no single person could initiate the mechanism and launch missiles.
4) According to the American Hazardous Substances Data Bank pentachlorobenzene is not
___________ as to human carcinogenicity because there are no human data and no animal data available.
5) ___________ these results as hard facts about the universe as we know it is premature.
6) Various cases of writers ___________ new technologies decades earlier are known to history.
7) Due to a fault in an algorithm, the program ceased to open ___________, it didn’t even react to
the click on it.
8) Scientific world had to ___________ particle-wave duality of light since it had both theoretical
and experimental proofs.
9) Despite models of light seeming ___________, each of them works perfectly.
10) Coal is to be ___________ by natural gas and nuclear power.
8. Change words in brackets so that they are grammatically correct for the sentence:
1) Survival to the age of 60 years with such complex cardiac malformations, ___________ by surgical
correction, is a rare occurrence. (modification)
2) The coordination problem is too important an issue to be kept ___________ off economist's research agenda. (definite)
3) Deciding upon a date of a conference without preceding discussion was ___________, that’s why
the organizers agreed to have a(n) ___________ where all details will be cleared. (point)
4) Tornadoes and hurricanes are too ___________ phenomena to be easily observed and studied.
(predict)
5) Increasing interest in the research of alternative sources of energy makes ___________ of traditional problematic ways of producing energy with new ones much more realistic. (place)
6) The uproar caused by his recent discovery is simply ___________: by the end of the day at least
three other laboratories have asked to repeat his experiments for the testimony. (description)
7) Federal and state costs for building and operating new laboratories ___________ to $25 billion.
(amount)
8) Since this method of evaluating the receptive-field center sizes is significantly different from ours,
these results are not straightforwardly ___________ to ours. (compare)
9) All his teammates get irritated with constant ___________ remarks of his; it was especially annoying on long conferences and plan making meetings. (time)
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10) In order to turn the deserts into fertile and ___________ land, engineers built an 900-mile canal.
(produce)
9. Translate the following word combinations into English:
1) определяется локальными условиями
2) дифференциальное уравнение
3) сконцентрированный в одной точке
4) на атомном уровне
5) по прямой
6) двигаться по определенной траектории
7) в заданной точке
8) с постоянной скоростью
9) перпендикулярный (по направлению) к
10) на препятствии
10. Find what word is suitable in all three sentences:
A 1 What temperature is required for mercury to become ___________?
2 Even though I had a(n) ___________ meal for dinner, by 5 o’clock I was hungry again.
3 Unfortunately, there are ___________ grounds to stop the work of this laboratory. It seems not to
meet safety requirements.
B 1 He is in ___________ of the project being carried out.
2 Rent cars are convenient for travelers, the only two things you need are an ID and to pay car hire
___________.
3 The Earth’s surface is known to have a negative ___________.
C 1 The company’s production ___________ has increased in the last 1.5 years.
2 How do you know an atomic ___________ of a chemical element?
3 Never mind that she’s sitting silently, look at her face — it speaks ___________.
11. Write a sentence with a set of words:
a) contradictory, entity, wave;
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