单选题
单选题
What aspect of the auroras does the class mainly discuss?
【正确答案】
D
【答案解析】[听力原文]
W1: For centuries, people have told stories to explain the moving lights in the night sky—the curtains of greenish-white light with pink fringe. People described these lights as the breath of the Earth, powerful spirits, or angel light. Early explorers wrote about the "bloody red" and "ghostly green" lights. These lights, of course, are the aurora borealis—the northern lights—and in the south, the aurora australis. Have any of you seen the auroras?
W2: I have. Several times when I lived in Alaska. I"ve photographed them, too. Mostly they were greenish-yellow, but once they were kind of purple. So beautiful!
W1: Most auroras are green or yellow or white, but sometimes they take colors from violet to pink to red. The auroras can be seen at any time of the year, with the right atmospheric conditions. They"re most often seen near the North and South Poles, during times of maximum solar activity. The closer to the North or South Pole you are, the better you can see the lights. The auroras occur in the ionosphere. The ionosphere is the layer of the upper atmosphere where, uh, where high—energy solar radiation strips electrons from oxygen and nitrogen atoms, and leaves them as positively charged ions. The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field. Here"s what happens. The sun"s heat charges the particles in the solar wind, a stream of electrically charged subatomic particles that continually emanates from the sun. As, uh, as the solar wind approaches Earth, it"s deflected by Earth"s magnetic field and diverted north and south towards the magnetic poles. The interaction between the solar wind and the magnetic field generates beams of electrons. These electrons collide with atoms and molecules within the ionosphere near Earth"s magnetic poles. The collisions rip apart molecules and excite atoms. So then oxygen and nitrogen atoms in the ionosphere become "excited," or ionized. The auroras happen when, uh, when these ionized atoms return to their normal state from their excited, energized states. The ions combine with free electrons. As they do so, they emit radiation. Part of this radiation is visible light: the aurora borealis and aurora australis. Yes, Simon?
M: Um...it"s just like electricity.
W1: Yes, that"s right. The auroras are an electrical phenomenon. As you know, an electrical generator has two components: a conductor and a magnetic field. To generate electricity, the conductor has to move across the field to produce a force. With the auroras, the conductor is the solar wind carrying a stream of charged particles.
M: So, what happens is, when, uh, when the charged particles reach Earth"s magnetic field, they, uh, move along in the field towards the North and South Poles. They collide with atmospheric gases, create a force, and eventually release the energy.
W1: Exactly. The particles collide with oxygen and nitrogen in the atmosphere, and the oxygen and nitrogen atoms get excited. And then, when the particles get de-excited and return to their normal state, they emit the auroras by releasing energy in the form of light. Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta. The activity of the auroras varies with the sun"s activity. When the sun is quiet, the auroras can be seen only in a small area. When the sun is active, however, the aurora borealis can be seen across southern Canada and the northern United States.
What aspect of the auroras does the class mainly discuss?
The class mainly discusses what causes the auroras. The professor says The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field. Here"s what happens; The auroras happen when these ionized atoms return to their normal state from their excited, energized states; ... they emit radiation. Part of this radiation is visible light: the aurora borealis and aurora australis.
W1: For centuries, people have told stories to explain the moving lights in the night sky—the curtains of greenish-white light with pink fringe. People described these lights as the breath of the Earth, powerful spirits, or angel light. Early explorers wrote about the "bloody red" and "ghostly green" lights. These lights, of course, are the aurora borealis—the northern lights—and in the south, the aurora australis. Have any of you seen the auroras?
W2: I have. Several times when I lived in Alaska. I"ve photographed them, too. Mostly they were greenish-yellow, but once they were kind of purple. So beautiful!
W1: Most auroras are green or yellow or white, but sometimes they take colors from violet to pink to red. The auroras can be seen at any time of the year, with the right atmospheric conditions. They"re most often seen near the North and South Poles, during times of maximum solar activity. The closer to the North or South Pole you are, the better you can see the lights. The auroras occur in the ionosphere. The ionosphere is the layer of the upper atmosphere where, uh, where high—energy solar radiation strips electrons from oxygen and nitrogen atoms, and leaves them as positively charged ions. The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field. Here"s what happens. The sun"s heat charges the particles in the solar wind, a stream of electrically charged subatomic particles that continually emanates from the sun. As, uh, as the solar wind approaches Earth, it"s deflected by Earth"s magnetic field and diverted north and south towards the magnetic poles. The interaction between the solar wind and the magnetic field generates beams of electrons. These electrons collide with atoms and molecules within the ionosphere near Earth"s magnetic poles. The collisions rip apart molecules and excite atoms. So then oxygen and nitrogen atoms in the ionosphere become "excited," or ionized. The auroras happen when, uh, when these ionized atoms return to their normal state from their excited, energized states. The ions combine with free electrons. As they do so, they emit radiation. Part of this radiation is visible light: the aurora borealis and aurora australis. Yes, Simon?
M: Um...it"s just like electricity.
W1: Yes, that"s right. The auroras are an electrical phenomenon. As you know, an electrical generator has two components: a conductor and a magnetic field. To generate electricity, the conductor has to move across the field to produce a force. With the auroras, the conductor is the solar wind carrying a stream of charged particles.
M: So, what happens is, when, uh, when the charged particles reach Earth"s magnetic field, they, uh, move along in the field towards the North and South Poles. They collide with atmospheric gases, create a force, and eventually release the energy.
W1: Exactly. The particles collide with oxygen and nitrogen in the atmosphere, and the oxygen and nitrogen atoms get excited. And then, when the particles get de-excited and return to their normal state, they emit the auroras by releasing energy in the form of light. Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta. The activity of the auroras varies with the sun"s activity. When the sun is quiet, the auroras can be seen only in a small area. When the sun is active, however, the aurora borealis can be seen across southern Canada and the northern United States.
What aspect of the auroras does the class mainly discuss?
The class mainly discusses what causes the auroras. The professor says The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field. Here"s what happens; The auroras happen when these ionized atoms return to their normal state from their excited, energized states; ... they emit radiation. Part of this radiation is visible light: the aurora borealis and aurora australis.
单选题
Why does the professor say this:
【正确答案】
C
【答案解析】[听力原文]
Why does the professor say this:
"The auroras can be seen at any time of the year, with the right atmospheric conditions. They"re most often seen near the North and South Poles, during times of maximum solar activity. The closer to the North or South Pole you are, the better you can see the lights."
The professor"s purpose is to point out where the auroras are most visible. She says They"re most often seen near the North and South Poles.... If you are closer to the North or South Pole, you will be better able to see them.
Why does the professor say this:
"The auroras can be seen at any time of the year, with the right atmospheric conditions. They"re most often seen near the North and South Poles, during times of maximum solar activity. The closer to the North or South Pole you are, the better you can see the lights."
The professor"s purpose is to point out where the auroras are most visible. She says They"re most often seen near the North and South Poles.... If you are closer to the North or South Pole, you will be better able to see them.
单选题
What is the professor"s main point about the auroras?
【正确答案】
B
【答案解析】[听力原文]
What is the professor"s main point about the auroras?
The professor"s main point is that the auroras result from the solar wind interacting with Earth"s magnetic field. She says The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field; The interaction between the solar wind and the magnetic field generates beams of electrons. These electrons collide with atoms and molecules within the ionosphere near Earth"s magnetic poles.
What is the professor"s main point about the auroras?
The professor"s main point is that the auroras result from the solar wind interacting with Earth"s magnetic field. She says The auroras are the result of a complex interaction between the solar wind and the Earth"s magnetic field; The interaction between the solar wind and the magnetic field generates beams of electrons. These electrons collide with atoms and molecules within the ionosphere near Earth"s magnetic poles.
单选题
Why does the professor say this:
【正确答案】
A
【答案解析】[听力原文]
Why does the professor say this:
"As you know, an electrical generator has two components: a conductor and a magnetic field. To generate electricity, the conductor has to move across the field to produce a force. With the auroras, the conductor is the solar wind carrying a stream of charged particles."
The professor"s purpose is to explain how the auroras are electrical in nature. The student says it"s just like electricity, and the professor responds by explaining how electricity is generated by the solar wind, carrying a stream of charged particles and moving across a magnetic field.
Why does the professor say this:
"As you know, an electrical generator has two components: a conductor and a magnetic field. To generate electricity, the conductor has to move across the field to produce a force. With the auroras, the conductor is the solar wind carrying a stream of charged particles."
The professor"s purpose is to explain how the auroras are electrical in nature. The student says it"s just like electricity, and the professor responds by explaining how electricity is generated by the solar wind, carrying a stream of charged particles and moving across a magnetic field.
多选题
Which of the following statements describe factors in the formation of auroras?
Click on 2 answers.
Click on 2 answers.
【正确答案】
A、C
【答案解析】[听力原文]
Which of the following statements describe factors in the formation of auroras?
One factor in the formation of auroras is that oxygen and nitrogen atoms in the ionosphere become "excited": ...oxygen and nitrogen atoms in the ionosphere become "excited," or ionized. Another factor is that charged particles de-energize and emit radiation as visible light: The auroras happen when these ionized atoms return to their normal state from their excited, energized states. The ions combine with free electrons. As they do so, they emit radiation. Part of this radiation is visible light....
Which of the following statements describe factors in the formation of auroras?
One factor in the formation of auroras is that oxygen and nitrogen atoms in the ionosphere become "excited": ...oxygen and nitrogen atoms in the ionosphere become "excited," or ionized. Another factor is that charged particles de-energize and emit radiation as visible light: The auroras happen when these ionized atoms return to their normal state from their excited, energized states. The ions combine with free electrons. As they do so, they emit radiation. Part of this radiation is visible light....
单选题
Listen again to part of the lecture. Then answer the question.
What can be inferred about the auroras?
What can be inferred about the auroras?
【正确答案】
B
【答案解析】[听力原文]
Listen again to part of the lecture. Then answer the question.
"The particles collide with oxygen and nitrogen in the atmosphere, and the oxygen and nitrogen atoms get excited. And then, when the particles get de—excited and return to their normal state, they emit the auroras by releasing energy in the form of light. Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta."
What can be inferred about the auroras?
The professor says Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta. You can infer that the color of auroras is related to the gas involved.
Listen again to part of the lecture. Then answer the question.
"The particles collide with oxygen and nitrogen in the atmosphere, and the oxygen and nitrogen atoms get excited. And then, when the particles get de—excited and return to their normal state, they emit the auroras by releasing energy in the form of light. Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta."
What can be inferred about the auroras?
The professor says Oxygen releases either dark red or ghostly green. Nitrogen emits rosy pink or magenta. You can infer that the color of auroras is related to the gas involved.