托福阅读历年真题精选35
Questions 30-40Most sources of illumination generate light over an appreciable period, and indeed if
an object is lit for a very brief time(less that 1/25 second), the human eye will not react
in time to see the object. A photographic emulsion---that is, a light-sensitive coating on photographic film, paper, or glass---will, however, record much shorter bursts of light. A
(5 ) photographic flash can therefore be used to capture high-speed movement on film as well
as to correct deficiencies of the normal surrounding lighting. Photoflash is now generated electronically, but the earliest form, first used in 1864, was a paper bag containing
magnesium wire and some oxygen-rich substance, such as potassium chlorate. When the
bag was ignited, the metal burned with an intense flash. A contemporary observer reported
(10) that “this quite unsafe device seems to have done nothing worse that engulf the room in
dense smoke and lead to pictures of dubious quality and odd poses.”
The evolution of the photoflash was slow, flashbulbs, containing fine wire made of a
metal, such as magnesium or aluminum, capable of being ignited in an atmosphere of pure oxygen at low pressure, were introduced only in the 1920’s. In the earliest type, the metal
(15) was separated from the oxygen by a thin glass bulb. The flash was fired by piercing the
bulb and allowing the oxygen to come into contact with the metal, which ignited
spontaneously. Later bulbs were fired by an electric battery, which heated the wire by
passing a small current through it. Other combinations, such as the pairing of oxygen
difluoride with zirconium, have also been used. In each case enough energy is given out to
(20) heat the oxidizable metal momentarily to a white-hot emission of visible light. The smoke particles are so small that they cool rapidly; but since they are white, they contribute to the brilliance by reflecting the light from their still-glowing neighbors. A slightly bigger form
of the metal will burn for a longer time.
30 What does the passage mainly discuss?
(A) The history of the photoflash
(B) Theories about how the eye reacts to light
(C) The technology of modern photography
(D) The dangers of using the early photoflash
31 According to the passage,1/25 second is the minimum amount of time required for the
(A) recording of an image on film
(B) generation of artificial light
(C) creation of a photographic emulsion
(D) human eye to react to light
托福阅读历年真题精选35
32 According to the passage, an advantage of using a photoflash is that it</p>(A) can produce repeated bursts of light(B) intensities colors in photographs
(C) is short enough not to bother human eyes
(D) supplements existing lighting
33 The word “ignited” in line 9 is closest in meaning to
(A) set on fire
(B) cut into
(C) opened
(D) shaken
34 Which of the following phrases is defined in paragraph 1?
(A)”appreciable period”(line 1)
(B)”photographic emulsion”(line 3)
(C)”high-speed movement”(line 5)
(D)”odd poses”(line 11)
35 The word “evolution” in line 12 is closest in meaning to
(A) publicity
(B) adoption
(C) development
(D) manufacture
36 The function of the glass in the first flashbulbs was to
(A) produce the spark that initiated the flash
(B) magnify the light produced by the flash
(C) protect the photographer from the heat of the flash
(D) keep the metal and oxygen apart before the flash
37 The word “it” in line 18 refers to
(A) oxygen
(B) battery
(C) wire
(D) current
38 The word “momentarily” in line 20 is closest in meaning to
(A) effortlessly
(B) briefly
(C) electronically
(D) gradually
39 According to the passage, the white color of the smoke particles generated by a flashbulb contributes to
(A) rapid cooling
(B) bright illumination
(C) electrical conductivity
(D) intense heat
40 According to the passage, a flashbulb can be made to burn longer by using
(A) thicker wire
(B) more oxygen
(C) thinner glass
(D) continuous electricity
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