官方真题Official3托福听力Lecture4文本+真题+答案解析

官方真题Official3托福听力Lecture4题目文本

1.What is the lecture mainly about?

a) Different ways of magnifying the spectrum of a star

b) How a chemical element was first discovered on the Sun

c) How astronomers identify the chemical elements in a star

d) Why the spectra of different stars are composed of different colors

2.What does the professor explain to one of the students about the term “radiation”?

a) It is defined incorrectly in the textbooks.

b) It was first used in the nineteenth century.

c) It is rarely used by astronomers.

d) It does not refer only to harmful energy.

3.What can be inferred about two stars if their spectra have similar spectral line patterns?

a) The stars are approximately the same distance from the Earth.

b) The stars probably have some chemical elements in common.

c) The stars have nearly the same brightness.

d) The stars are probably of the same size.

4.According to the professor, what is the purpose of heating an element in a spectroscopic flame test?

a) To cause an element to emit light

b) To study an element in combination with other elements

c) To remove impurities from the element

d) To measure an element’s resistance to heat

5.Why does the professor say this?

a) He is about to provide some background information.

b) He is about to repeat what he just said.

c) He intends to focus on the history of astronomy.

d) He intends to explain two different points of view.

6.Why does the professor ask this?

a) To check the students’ understanding of their reading assignment

b) To give the students a hint to the answer to his previous question

c) To emphasize how important it is for astronomers to study Greek

d) To remind the students about the historical background of astronomy

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