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Файл:English for Optics Students. Английский для студентов, изучающих оптику. Учебное пособие
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there's one optimum spot where you should hit the water. This is analogous
to the cause of bending in light when it travels from one environment to
another in which the speed of distribution of light is different.
Text 4
Clinical significance
In medicine, particularly optometry, ophthalmology and orthoptics,
refraction (also known as refractometry) is a clinical test in which a phoropter may be used by the appropriate eye care professional to determine the
eye's refractive error and the best corrective lenses to be prescribed. A series
of test lenses in graded optical powers or focal lengths are presented to
determine which provides the sharpest, clearest vision.
[4]
Acoustics
In underwater acoustics, refraction is the bending or curving of a sound
ray that results when the ray passes through a sound speed gradient from a
region of one sound speed to a region of a different speed. The amount of
ray bending is dependent upon the amount of difference between sound
speeds, that is, the variation in temperature, salinity, and pressure of the
water. Similar acoustics effects are also found in the Earth's atmosphere.
The phenomenon of refraction of sound in the atmosphere has been known
for centuries; however, beginning in the early 1970s, widespread analysis of
this effect came into vogue through the designing of urban highways and
noise barriers to address the meteorological effects of bending of sound rays
in the lower atmosphere.
31
UNIT PHYSICAL OPTICS
Terminology
aperture
approximation
coherence
concave
convex
creeping wave
light disturbance
lossy surfaces
orthogonal
perturbation
quantum mechanical effects
scatter
electromagnetic waves
Task 1. Explain the following words.
propagate, geometric optics, medium, quantum, approximation,
Task 2. Match the words 1- to their meanings A-K.
1 valid
2 tend
3 treat
4 orthogonal
5 disturbance
6 intermediate
7 estimate
8 perturbation
9 aperture
10 creeping wave
11 shadow
A оценивать
B раскрыв, расходимость
C прямоугольный
D возмущение, помехи
E тень
F действительный, имеющий силу
G возмущение, нарушение
H ползущая/скользящая/ползучая волна
I рассматривать
J иметь тенденцию, быть склонным
K промежуточный
Task 3. Answer the questions.
1. How does light propagate?
2. What can the length of the light wave be?
3. What types can optics be divided into? Why?
4. When did the Elliott Wave Principle appear? Why?
5. What do you know about the creeping wave?
32
Task 4. Read the text and fill in the gaps with the following word combinations. Entitle the text.
are not explained
are now generally treated
believed
can be used
is also often applied
is approximately
is not valid
is then obtained
is used to estimate
propagate
tends not to include
was predicted
is considered to propagate
1. In physical optics, light 1 … as a wave. This model predicts phenomena such as interference and diffraction, which 2 … by geometric optics.
The speed of light waves in air 3 … 3.0×10
8
m/s (exactly 299,792,458 m/s
in vacuum). The wavelength of visible light waves varies between 400 and
700 nm, but the term "light" 4 … to infrared (0.7–300 μm) and ultraviolet
radiation (10–400 nm).
2 The wave model 5 … to make predictions about how an optical system will behave without requiring an explanation of what is "waving" in
what medium. Until the middle of the 19th century, most physicists 6 … in
an "ethereal" medium in which the light disturbance propagated. The
existence of electromagnetic waves 7 … in 1865 by Maxwell's equations.
These waves 8 … at the speed of light and have varying electric and magnetic fields which are orthogonal to one another, and also to the direction of
propagation of the waves. Light waves 9 … as electromagnetic waves except when quantum mechanical effects have to be considered.
3 In physics, physical optics, or wave optics, is the branch of optics
which studies interference, diffraction, polarization, and other phenomena
for which the ray approximation of geometric optics 10 …. This usage
11 … effects such as quantum noise in optical communication, which is
studied in the sub-branch of coherence theory.
4 Physical optics is also the name of an approximation commonly used
in optics, electrical engineering and applied physics. In this context, it is an
intermediate method between geometric optics, which ignores wave effects,
and full wave electromagnetism, which is a precise theory. The word
"physical" means that it is more physical than geometric or ray optics and
not that it is an exact physical theory. This approximation consists of using
ray optics to estimate the field on a surface and then integrating that field
over the surface to calculate the transmitted or scattered field. This resem-
33
bles the Born approximation, in that the details of the problem are treated as
a perturbation.
5 In optics, it is a standard way of estimating diffraction effects.
In radio, this approximation 12 … some effects that resemble optical
effects. It models several interference, diffraction and polarization effects
but not the dependence of diffraction on polarization. Since it is a high frequency approximation, it is often more accurate in optics than for radio.
In optics, it typically consists of integrating ray estimated field over a lens,
mirror or aperture to calculate the transmitted or scattered field.
6 In radar scattering it usually means taking the current that would be
found on a tangent plane of similar material as the current at each point on
the front, i. e. the geometrically illuminated part, of a scatterer. Current on
the shadowed parts is taken as zero. The approximate scattered field 13 …
by an integral over these approximate currents. This is useful for bodies
with large smooth convex shapes and for lossy (low reflection) surfaces.
7 The ray optics field or current is generally not accurate near edges or
shadow boundaries, unless supplemented by diffraction and creeping wave
calculations. The standard theory of physical optics has some defects in the
evaluation of scattered fields, leading to decreased accuracy away from the
specular direction. An improved theory introduced in 2004 gives exact solutions to problems involving wave diffraction by conducting scatterers.
(https://en.wikipedia.org/wiki/Physical_optics)
Task 5. Match paragraphs 1–7 to subtitles A-H. One subtitle is extra.
A Scattering
B Approximation in radio
C The background of the subject
D Wavelengths
E The problem of inaccuracy
F The nature of light waves
G The subject of physical optics
H Some branches of physics
Task 6. What do the following numbers mean?
8
3,0 × 10
299,792,458 400–700
0,7–300 19 2004
10–400 1865
Task 7. What do the following abbreviations mean?
m/s nm μm
34
Task 8. Work with a partner to complete the word families in the table
below. Translate them into Russian.
Verb Noun (doer) Noun Adjective, Participle
…
…
…
improve
…
supplement
…
…
scatter
…
…
calculate
resemble
-
…
..
…
…
–
…
…
…
…
…
…
–
…
evaluation
...
…
polarization
…
…
…
…
…
…
…
…
involving
…
approximate
…
…
…
leading
illuminated
…
estimated
integrating
…
…
Task 9. Work in pairs. Choose any 7 words from the table above and
write down 7 questions about physical optics using the words chosen. Ask
the questions to your partner.
E.g. What does scattering mean?
Task 10. Define the grammar form of the verbs given in Task 4.
Translate the sentences from the text where these verbs are used.
Task 11. What grammar phenomenon is used in the following sentence?
In physical optics light is considered to propagate as a wave.
Task 12. Refresh your knowledge of the grammar phenomenon Complex Subject.
Grammar references
Complex Subject
Конструкция Complex Subject в английском языке применяется с
определенными глаголами. Эти глаголы условно можно разделить на
несколько групп. Итак, в качестве сказуемого в предложении могут
использоваться глаголы, выражающие:
1. Осведомленность, знание, утверждение: to know (
знать), to think
(думать), to state (заявлять, утверждать), to report (сообщать), to say
(говорить), to announce (сообщать).
35
She is known to live in France. – Известно, что она живет во Фран-
ции.
The film festival was reported to take place in July this year. – Сообщали, что кинофестиваль пройдет в июле в этом году.
He was thought to study here. – Думали, что он учится здесь.
2. Предположение: to expect (ожидать), to suppose (предполагать),
to believe (верить), to consider (считать, полагать), to ask (спрашивать).
The student is expected to become a famous writer. – Ожидают, что
этот студент станет известным писателем.
The tickets were supposed to be sold in the afternoon. – Предполагали,
что билеты продадут днём.
3.
Восприятие: to see (видеть), to hear (слышать), to notice (отме-
чать).
The car was seen to disappear. – Видели, как машина скрылась.
She was seen to enter. – Видели, как она вошла.
4. Также Complex Subject в английском языке используется после
таких словосочетаний, как to be likely (вероятно), to be unlikely (маловероятно), to be certain (несомненно), to be sure (обязательно).
She is likely to succeed. – Вероятно, ее ждет успех.
The bag is not likely to have been stolen. – Маловероятно, что сумку
украли.
Все перечисленные глаголы, будучи
сказуемыми, могут быть использованы в любом времени, но только в страдательном (пассивном)
залоге – Passive voice.
Есть еще группа глаголов, которые употребляются с конструкцией
Complex Subject в английском языке, но в действительном (активном –
Active voice) залоге. Это следующие глаголы: to appear – появляться,
казаться, оказаться; to seem – казаться; to happen – случаться; to prove /
to turn out – оказаться.
The second part of the movie appeared to be less interesting. – Оказа-
лось, что
вторая часть фильма не такая интересная.
He seems to be sleeping. – Кажется, что он спит.
На самом деле, конструкции Complex Object и Complex Subject не
представляют никакой сложности, а, наоборот, облегчают нашу речь,
делая ее более похожей на англоязычную, а не на речь родного языка.
Они очень популярны и употребляются повсеместно, поэтому постарайтесь не обойти их
стороной, а уделить им внимание.
36
Task 13. Translate the following sentences. Keep in mind the pecu-
liarities of translation Complex Object и Complex Subject into Russian.
1. Alpha-rays were shown to be identical, no matter from what radioac-
tive element they are emitted.
2. At first the alpha-rays were thought to be undeviated by the magnetic
fields.
3. Light is considered to be some kind of wave motion of electromag-
netic origin.
4. The people from the Institute of Optics are known to be working hard
at a new device.
5. The light from stars is known to be coming to us during millions of
years.
6. Ancient Greeks seem to have manufactured the first lens.
Task 14. Continue your pair work. One of you is Student A and the
other is Student B. Read the corresponding task and talk to your partner.
Student A: You are a journalist of a students’ newspaper. Have an inter-
view with a senior student of optics to find out what interference, diffraction, polarization mean and what fields they are used in.
Student B: You are a senior student of optics. Get ready to answer the
questions of a journalist about interference, diffraction and polarization.
Task 15. Discuss with your partner the meaning of the term “physical
optics”, the main notions of the field and their application.
Task 16. Write an essay of 150 words on the topic “Tasks of physical
optics”. Read your essay and share your ideas with the class.
Additional tasks to unit Physical Optics
Task 1. Match the words to their meanings.
1 smear out
2 rate
3 finite
4 arbitrary
5 duality
6 quanta
A произвольный, случайный
B двойственность
C зд. размывать
D скорость, норма, темп
E кванты
F конечный
37
Task 2. Answer the questions.
1. What theories of light are there? Explain each of them.
2. When did they appear?
3. What is the difference between those theories?
4. What experiments prove each of those theories?
5. What laws lie in their basis?
Task 3. Read the text below and entitle it and each of its paragraphs.
The German scientist Max Planck suggested in 1900 that light, X rays,
and other waves could not be emitted at an arbitrary rate, but only in certain
packets that he called quanta. Moreover, each quantum had a certain amount
of energy that was greater the higher the frequency of the waves, so at a
high enough frequency the emission of a single quantum would require
more energy than was available. Thus the radiation at high frequencies
would be reduced, and so the rate at which the body lost energy would be
finite.
The quantum hypothesis explained the observed rate of emission of ra-
diation from hot bodies very well, but its implications for determinism were
not realized until 1926, when another German scientist, Werner Heisenberg,
formulated his famous uncertainty principle. In order to predict the future
position and velocity of a particle, one has to be able to measure its present
position and velocity accurately. The obvious way to do this is to shine light
on the particle.
Some of the waves of light will be scattered by the particle and this will
indicate its position. However, one will not be able to determine the position
of the particle more accurately than the distance between the wave crests of
light, so one needs to use light of a short wavelength in order to measure the
position of the particle precisely. Now, by Planck’s quantum hypothesis,
one cannot use an arbitrarily small amount of light; one has to use at least
one quantum. This quantum will disturb the particle and change its velocity
in a way that cannot be predicted. Moreover, the more accurately one
measures the position, the shorter the wavelength of the light that one needs
and hence the higher the energy of a single quantum. So the velocity of the
particle will be disturbed by a larger amount. In other words, the more accurately you try to measure the position of the particle, the less accurately you
can measure its speed, and vice versa.
Although light is made up of waves, Planck’s quantum hypothesis tells
us that in some ways it behaves as if it were composed of particles: it can be
38
emitted or absorbed only in packets, or quanta. Equally, Heisenberg’s uncertainty principle implies that particles behave in some respects like waves:
they do not have a definite position but are “smeared out” with a certain
probability distribution. The theory of quantum mechanics is based on an
entirely new type of mathematics that no longer describes the real world in
terms of particles and waves; it is only the observations of the world that
may be described in those terms.
There is thus a duality between waves and particles in quantum mecha-
nics: for some purposes it is helpful to think of particles as waves and for
other purposes it is better to think of waves as particles. An important consequence of this is that one can observe what is called interference between
two sets of waves or particles. That is to say, the crests of one set of waves
may coincide with the troughs of the other set. The two sets of waves then
cancel each other out rather than adding up to a stronger wave as one might
expect.
(A Brief History of Time - Stephen Hawking... Chapter 4
http://www.fisica.net/relatividade/stephen_hawking_a_brief_history_of
_time.pdf)
Task 4. Look through the text and find the names of people who con-
tributed to developing optics. What do you know about those people?
Search the Internet to learn more about them. Share what you have found
with the group.
Task 5. Match the words to their synonyms.
1 obvious
2 cancel
3 observe
4 consequence
5 accurately
6 predict
A foresee
B results
C precisely
D annul
E watch
F clear
Task 6. Find and translate the sentences in the text of Task 3, where
the following linking words are used.
vice versa, hence, that is to say, although, thus, equally, moreover, so, in
order to, however.
Task 7. Make sentences of your own using the linking words from
Task 6.
39
Task 8. Work with a partner to complete the word families in the table
S
below. Translate them into Russian.
Noun Adjective Adverb Verb
…
frequency
uncertainty
duality
…
…
…
measure
…
…
observation
…
…
…
…
…
…
…
disturbed
…
absorbed
realized
…
…
arbitrarily
…
…
…
–
–
–
–
–
–
–
…
…
…
–
–
imply
reduce
…
…
…
…
...
coincide
Task 9. Work in pairs. Choose any 7 words from the table above and
make and write down 7 questions about optics using the words chosen.
Ask the questions to your partner.
Task 10. Fill in the table using the text of Task 3 and the text below.
Particles theory Wave theory
Date of appearance
cientists who contributed
to the theory development
Foundation of the theory
Proofs of the theory
Any other details
We could still imagine that there is a set of laws that determine events
completely for some supernatural being, who could observe the present state
of the universe without disturbing it. However, such models of the universe
are not of much interest to us ordinary mortals. It seems better to employ the
principle of economy known as Occam’s razor and cut out all the features of
the theory that cannot be observed. This approach led Heisenberg, Erwin
Schrodinger, and Paul Dirac in the 1920s to reformulate mechanics into a
new theory called quantum mechanics, based on the uncertainty principle.
In this theory particles no longer had separate, well-defined positions and
40
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