Câu hỏi:
11/04/2020 1,195Read the passage and mark the letter A, B, C or D to answer the following questions.
Most sources of illumination generate light over an appreciable period, and indeed if an object is lit for a very brief time (1ess 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 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 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 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 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.
Which of the following most accurately reflects the main idea of the last paragraph?
Đáp án chính xác
Câu hỏi trong đề:
30 đề thi thử đề thi thử THPTQG môn Tiếng Anh có lời giải chi tiết !!
Sách mới 2k7: Tổng ôn Toán, Lí, Hóa, Văn, Sử, Địa…. kỳ thi tốt nghiệp THPT Quốc gia 2025, đánh giá năng lực (chỉ từ 110k).
Quảng cáo
Trả lời:
Giải bởi Vietjack
Đáp án C
Câu nào dưới đây phản ảnh chính xác nhất ý chính của đoạn cuối?
A. Đèn flash lần đầu tiên được sử dụng là khi nào.
B. Làm sao kim loại cháy được trong môi trường oxy tinh khiết.
C. Cách thức hoạt động của đèn flash đời đầu.
D. Vai trò của thủy tinh trong bóng đèn flash.
Căn cứ vào thông tin trong đoạn cuối: đã được trích dẫn trong các câu 38, 39, và 40, ta dễ dàng nhận thấy đoạn này nói về cách tạo ra tia flash ở loại đèn flash đời đầu tiên.
Nhà sách VIETJACK:
CÂU HỎI HOT CÙNG CHỦ ĐỀ
Câu 1:
Local authorities should find ways to limit the use of private cars and encourage city _____ to use public transport.
Xem đáp án »
11/04/2020
86,176
Câu 2:
_____ the email - supposedly from Boyd's Bank - to be genuine, she was tricked into disclosing her credit card details.
Xem đáp án »
11/04/2020
80,808
Câu 3:
This safe, _____ friendly city is like a paradise for its inhabitants who can enjoy the highest quality of life.
Xem đáp án »
11/04/2020
73,795
Câu 4:
Mark the letter A, B, C, or D to indicate the word(s) CLOSEST in meaning to the underlined word (5) in each of the following questions.
Young college and university students participate in helping the poor who have suffered badly in wars or natural disasters.
Xem đáp án »
11/04/2020
71,637
Câu 5:
My brother has applied for that scholarship for months, but he has never succeeded yet.
Xem đáp án »
11/04/2020
67,275
Câu 6:
Mark the letter A, B, C, or D to indicate the word(s) CLOSEST in meaning to the underlined word (5) in each of the following questions.
Life expectancy for both men and women has improved greatly in the past twenty years.
Xem đáp án »
11/04/2020
58,971
Câu 7:
When I got to 16, some of my friends left school to get a job, but most _____.
Xem đáp án »
11/04/2020
50,232
về câu hỏi!