学历教育 - 英语考试
The letter without the address puzzled me.
A:perplexed
B:interested
C:troubled
D:enlightened
查看答案
A:perplexed
B:interested
C:troubled
D:enlightened
共用题干
Giant Structures
It is an impossible task to select the most amazing wonders of the modern world since every year more______(1)constructions appear. Here are three giant structures which are worthy of our admiration______(2)they may have been surpassed by some more recent wonders.
The Petronas Twin Towers
The Petronas Towers were the tallest buildings in the world when they were completed in 1999.______(3)a height of 452 metres,the tall twin towers,like two thin pencils,dominate the city of Kuala Lumpur. At the 41st floor,the towers are______(4)by a bridge,symbolizing a gateway to the city. The American architect Cesar Pelli designed the skyscrapers.
Constructed of high-strength concrete,the building______(5)around 1,800 square metres of office space on every floor. And it has a shopping centre and a concert hall at the base.Other______(6)of this impressive building include double-decker lifts,and glass and steel sunshades.
The Millau Bridge
The Millau Bridge was opened in 2004 in the Tarn Valley,in southern France. At the ______(7)it was built,it was the world,5 highest bridge,______(8)over 340m at the highest point. The bridge is described as one of the most amazingly beautiful bridges in the world. It was built to ________ (9) Millau's congestion（拥堵）problems. The congestion was then caused by traffic passing from Paris to Barcelona in Spain. The bridge was built to with-stand the______(10) extreme seismic（地震的）and climatic conditions. Besides , it is guar- anteed for 120 years!
The Itaipu Dam
The Itaipu hydroelectric power plant is one of the largest constructions of its kind in the world.
It______(11)of a series of dams across the River Parana,______(12)forms a natural border between Brazil and Paraguay. Started in 1975 and taking 16 years to complete, the construction was carried out as a joint project between the two______(13).The dam is well-known for both its electricity output and its size. In 1995 it produced 78% of Paraguay's and 25% Of Brazil's______(14)needs. In its construction,the amount of iron and steel used was equivalent to over 300 Eiffel Towers.It is a______(15)amazing wonder of engineering.
2._________
A: when
B: although
C: if
D: because
查看答案
Giant Structures
It is an impossible task to select the most amazing wonders of the modern world since every year more______(1)constructions appear. Here are three giant structures which are worthy of our admiration______(2)they may have been surpassed by some more recent wonders.
The Petronas Twin Towers
The Petronas Towers were the tallest buildings in the world when they were completed in 1999.______(3)a height of 452 metres,the tall twin towers,like two thin pencils,dominate the city of Kuala Lumpur. At the 41st floor,the towers are______(4)by a bridge,symbolizing a gateway to the city. The American architect Cesar Pelli designed the skyscrapers.
Constructed of high-strength concrete,the building______(5)around 1,800 square metres of office space on every floor. And it has a shopping centre and a concert hall at the base.Other______(6)of this impressive building include double-decker lifts,and glass and steel sunshades.
The Millau Bridge
The Millau Bridge was opened in 2004 in the Tarn Valley,in southern France. At the ______(7)it was built,it was the world,5 highest bridge,______(8)over 340m at the highest point. The bridge is described as one of the most amazingly beautiful bridges in the world. It was built to ________ (9) Millau's congestion（拥堵）problems. The congestion was then caused by traffic passing from Paris to Barcelona in Spain. The bridge was built to with-stand the______(10) extreme seismic（地震的）and climatic conditions. Besides , it is guar- anteed for 120 years!
The Itaipu Dam
The Itaipu hydroelectric power plant is one of the largest constructions of its kind in the world.
It______(11)of a series of dams across the River Parana,______(12)forms a natural border between Brazil and Paraguay. Started in 1975 and taking 16 years to complete, the construction was carried out as a joint project between the two______(13).The dam is well-known for both its electricity output and its size. In 1995 it produced 78% of Paraguay's and 25% Of Brazil's______(14)needs. In its construction,the amount of iron and steel used was equivalent to over 300 Eiffel Towers.It is a______(15)amazing wonder of engineering.
2._________
A: when
B: although
C: if
D: because
共用题干
第一篇
The Northern Lights
The sun is stormy and has its own kind of weather.It is so hot and active that even the Sun's gravity cannot hold its atmosphere in check!Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour.These particles are called plasma （等离子体）,and the stream of plasma coming from the Sun is called the solar wind.The more active the Sun,the stronger the solar wind.
The solar wind constantly streams toward the Earth,but don't worry because a protective magnetic field surrounds our planet.The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles.The charged particles become trapped in magnetic belts around the Earth.When a large blast of solar wind crashes into the Earth's magnetic field,the magnetic field first gets squeezed and then the magnetic field lines break and reconnect.The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into tile Earth's atmosphere at the poles.As the electrons fall to the Earth,they collide with gas molecules in the atmosphere,creating flashes of light in the sky.
Each atmospheric gas glows a different color.Oxygen and nitrogen glows red and green arid nitrogen glows violet purple.As these various colors glow and dance in the night sky,they create the Northern Lights and the Southern Lights.
Watching auroras（北极光）is fun and exciting, but normally you can only see them in places far north like Alaska and Canada.The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate（跳动）,flicker（闪烁）,or even move like waves.During solar maximum,5 auroras are seen as far south as Florida,even Mexico!Auroras often seem to be very close to the ground,but the lowest aurora is still about 100 kilometers above the ground,a distance much higher than clouds are formed or airplanes can fly.A typical aurora band can be thousands of kilometers long,a few hundred kilometers high,but only a few hundred meters thick.
We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime.We know you will never forget it!
The solar wind comes into being as a result of_______.
A:disappearance of the Sun's gravity
B:unpredictable weather of the Sun
C:fast flow of energy away from the Sun
D:a stream of particles being blown away
查看答案
第一篇
The Northern Lights
The sun is stormy and has its own kind of weather.It is so hot and active that even the Sun's gravity cannot hold its atmosphere in check!Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour.These particles are called plasma （等离子体）,and the stream of plasma coming from the Sun is called the solar wind.The more active the Sun,the stronger the solar wind.
The solar wind constantly streams toward the Earth,but don't worry because a protective magnetic field surrounds our planet.The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles.The charged particles become trapped in magnetic belts around the Earth.When a large blast of solar wind crashes into the Earth's magnetic field,the magnetic field first gets squeezed and then the magnetic field lines break and reconnect.The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into tile Earth's atmosphere at the poles.As the electrons fall to the Earth,they collide with gas molecules in the atmosphere,creating flashes of light in the sky.
Each atmospheric gas glows a different color.Oxygen and nitrogen glows red and green arid nitrogen glows violet purple.As these various colors glow and dance in the night sky,they create the Northern Lights and the Southern Lights.
Watching auroras（北极光）is fun and exciting, but normally you can only see them in places far north like Alaska and Canada.The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate（跳动）,flicker（闪烁）,or even move like waves.During solar maximum,5 auroras are seen as far south as Florida,even Mexico!Auroras often seem to be very close to the ground,but the lowest aurora is still about 100 kilometers above the ground,a distance much higher than clouds are formed or airplanes can fly.A typical aurora band can be thousands of kilometers long,a few hundred kilometers high,but only a few hundred meters thick.
We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime.We know you will never forget it!
The solar wind comes into being as a result of_______.
A:disappearance of the Sun's gravity
B:unpredictable weather of the Sun
C:fast flow of energy away from the Sun
D:a stream of particles being blown away
共用题干
Homosexuals（同性恋者）
Many homosexuals prefer to be called gay or,for woman,lesbian.Most of them live quiet lives just______(51)anyone else.Some gay people have always raised children,______(52)or with partners,and the use of artificial insemination（人工受精）is increasing among lesbians.
Gay persons are in every kind of job.Some are very open about their homosexuality,and some are more private.Some______(53)their sexual orientation as a biological given and others as a choice.For those women who see it as a choice,one reason often given is the inequality in most heterosexual（异性恋的）relationships.
Homosexuality has been common in most cultures throughout history and generally______ (54).As a result,homosexual activity became a crime,______(55)which the penalty in early courts was death.Homosexual behavior is still______(56)in many countries and the United States.
Homosexuality later came to be viewed widely as less a sin than a sickness,but now no mentalhealth professional（具有专业资格的人）any longer ______ (57) homosexuality an illness. More recent theories to______(58)for homosexuality have included those based on biological and sociological factors.To date.______(59),there is no conclusive general theory that can explain the cause of homosexuality.
Attitudes______(60)homosexuality began to change in the second half of the 20th century. Gays attribute this,in part,to their own struggle for their rights and pride in their orientation. Some large companies now______(61)health-care benefits to the life partners of their gay employees. Many cities also have officially appointed lesbian and gay advisory（咨询的）committees.______(62)some attitudes have changed,however,prejudice（偏见）still exists,and in the late 1980s and early 1990s,there were considerable shouts against homosexuals,with attempt to ______(63)laws forbidding the granting of basic civil rights to gays.
The AIDS epidemic,which started in the 1980s,has devastated（毁坏）the gay community and brought it together as never before,The organized gay response to the lack of government financial support for fighting AIDS and to the needs of the thousands of AIDS victim______(64)they be gays or not,has been a model of community action.AIDS,however,has also______(65)people with another reason for their prejudice.
_________(52)
A:lone
B:lonely
C:along
D:alone
查看答案
Homosexuals（同性恋者）
Many homosexuals prefer to be called gay or,for woman,lesbian.Most of them live quiet lives just______(51)anyone else.Some gay people have always raised children,______(52)or with partners,and the use of artificial insemination（人工受精）is increasing among lesbians.
Gay persons are in every kind of job.Some are very open about their homosexuality,and some are more private.Some______(53)their sexual orientation as a biological given and others as a choice.For those women who see it as a choice,one reason often given is the inequality in most heterosexual（异性恋的）relationships.
Homosexuality has been common in most cultures throughout history and generally______ (54).As a result,homosexual activity became a crime,______(55)which the penalty in early courts was death.Homosexual behavior is still______(56)in many countries and the United States.
Homosexuality later came to be viewed widely as less a sin than a sickness,but now no mentalhealth professional（具有专业资格的人）any longer ______ (57) homosexuality an illness. More recent theories to______(58)for homosexuality have included those based on biological and sociological factors.To date.______(59),there is no conclusive general theory that can explain the cause of homosexuality.
Attitudes______(60)homosexuality began to change in the second half of the 20th century. Gays attribute this,in part,to their own struggle for their rights and pride in their orientation. Some large companies now______(61)health-care benefits to the life partners of their gay employees. Many cities also have officially appointed lesbian and gay advisory（咨询的）committees.______(62)some attitudes have changed,however,prejudice（偏见）still exists,and in the late 1980s and early 1990s,there were considerable shouts against homosexuals,with attempt to ______(63)laws forbidding the granting of basic civil rights to gays.
The AIDS epidemic,which started in the 1980s,has devastated（毁坏）the gay community and brought it together as never before,The organized gay response to the lack of government financial support for fighting AIDS and to the needs of the thousands of AIDS victim______(64)they be gays or not,has been a model of community action.AIDS,however,has also______(65)people with another reason for their prejudice.
_________(52)
A:lone
B:lonely
C:along
D:alone
共用题干
Mother Nature Shows Her Strength
Tornadoes（龙卷风）and heavy thunderstorms moved across the Great Lakes and into
Trumbull County on Saturday evening.The storms were dramatic and dangerous.
George Snyder was driving the fire truck down Route 88 when he first noticed that a
funnel（漏斗状的）cloud was behind him. " I stopped the truck and watched the funnel
cloud.It was about 1 00 feet off the ground and I saw it go up and down for a while.It was
moving toward Bradley Road and then suddenly it disappeared,"Snyder said.
Snyder only saw one of the funnel clouds that passed through northeastern Ohio on
Saturday.In Trumbull County,a tornado turned trees onto their sides.Some trees fell onto
houses and cars.Other trees fell into telephone and electrical wires as they went down.
Amanda Symcheck was having a party when the storm began."I knew something was
wrong , " she said."I saw the sky go green and pink（粉红色）.Then it sounded like a
train rushing toward the house.I started crying and told everyone to go to the basement for
protection."
The tornado caused a lot of damage to cars and houses in the area.It will take a long
time and much money to repair everything.There was also serious water damage from the
thunderstorms.The heavy rains and high wind caused the power to go out in many homes.
The storms caused serious flooding in areas near the river. More than four inches of
rain fell in parts of Trumbull County.The river was so high that the water ran into streets
and houses.Many streets had to be closed to cars and trucks because of the high water.
This made it difficult for fire trucks,police cars,and other rescue vehicles to help people
who were in trouble.
Many people who live near the river had to leave their own safety.
Some people reported five feet of water in their homes.Local and state officials opened
emergency shelters for the people who were evacuated(撤走).The Red Cross served meals to them.
"This was a really intense storm,"said Snyder."People were afraid.Mother Nature can be fierce.We were lucky this time.No one was killed."
Rescue vehicles had a hard time getting to people.
A:Right
B:Wrong
C:Not mentioned
查看答案
Mother Nature Shows Her Strength
Tornadoes（龙卷风）and heavy thunderstorms moved across the Great Lakes and into
Trumbull County on Saturday evening.The storms were dramatic and dangerous.
George Snyder was driving the fire truck down Route 88 when he first noticed that a
funnel（漏斗状的）cloud was behind him. " I stopped the truck and watched the funnel
cloud.It was about 1 00 feet off the ground and I saw it go up and down for a while.It was
moving toward Bradley Road and then suddenly it disappeared,"Snyder said.
Snyder only saw one of the funnel clouds that passed through northeastern Ohio on
Saturday.In Trumbull County,a tornado turned trees onto their sides.Some trees fell onto
houses and cars.Other trees fell into telephone and electrical wires as they went down.
Amanda Symcheck was having a party when the storm began."I knew something was
wrong , " she said."I saw the sky go green and pink（粉红色）.Then it sounded like a
train rushing toward the house.I started crying and told everyone to go to the basement for
protection."
The tornado caused a lot of damage to cars and houses in the area.It will take a long
time and much money to repair everything.There was also serious water damage from the
thunderstorms.The heavy rains and high wind caused the power to go out in many homes.
The storms caused serious flooding in areas near the river. More than four inches of
rain fell in parts of Trumbull County.The river was so high that the water ran into streets
and houses.Many streets had to be closed to cars and trucks because of the high water.
This made it difficult for fire trucks,police cars,and other rescue vehicles to help people
who were in trouble.
Many people who live near the river had to leave their own safety.
Some people reported five feet of water in their homes.Local and state officials opened
emergency shelters for the people who were evacuated(撤走).The Red Cross served meals to them.
"This was a really intense storm,"said Snyder."People were afraid.Mother Nature can be fierce.We were lucky this time.No one was killed."
Rescue vehicles had a hard time getting to people.
A:Right
B:Wrong
C:Not mentioned
共用题干
Cell Phone Lets Your Secret Out
Your cell phone holds secrets about you.Besides the names and _____________(51)that you've pro-
grammed into it,traces of your DNA linger on the device,according to a new study.
DNA is genetic material that______________(52)in every cell.Like your fingerprint,your DNA is unique
to you一 _____________（53)you have an identical twin.Scientists today routinely analyze DNA in blood,
saliva,or hair left _____________(54)at the scene of a crime.The results often help detectives identify
_____________(55)and their victims.Your cell phone can reveal more about you _____________(56)you might
think.
Meghan J.McFadden,a scientist at McMaster University in Hamilton,Ontario,heard about a crime in
which the suspect bled onto a cell phone and later dropped the______________(57).This made her wonder
whether traces of DNA lingered on cell phones even when no blood was involved.______________(58)she and
colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volun-
teers.They used swabs to collect______________(59)traces of the users from two parts of the phone:the
outside,where the user holds it,and the______________(60),which is placed at the user's ear.
The scientists scrubbed the phones using a solution made mostly______________(61)alcohol.The aim of
washing was to remove all detectable traces of DNA.The owners got their phones______________(62)for
another week.Then the researchers collected the phones and repeated the swabbing of each phone once
more.
The scientists discovered DNA that _____________(63)to the phone's speaker on each of the phones.
Better samples were collected from the outside of each phone,but those swabs also picked up DNA that be-
longed to other people who had apparently also handled the phone.______________(64),DNA showed up even
in swabs that were taken immediately after the phones were scrubbed.That suggests that washing won't remove
all traces of evidence from a criminal's device.So cell phones can now be added to the
______________(65)of clues
that can clinch a crime-scene investigation.
_________(65)
A:explanation
B:discovery
C:book
D:list
查看答案
Cell Phone Lets Your Secret Out
Your cell phone holds secrets about you.Besides the names and _____________(51)that you've pro-
grammed into it,traces of your DNA linger on the device,according to a new study.
DNA is genetic material that______________(52)in every cell.Like your fingerprint,your DNA is unique
to you一 _____________（53)you have an identical twin.Scientists today routinely analyze DNA in blood,
saliva,or hair left _____________(54)at the scene of a crime.The results often help detectives identify
_____________(55)and their victims.Your cell phone can reveal more about you _____________(56)you might
think.
Meghan J.McFadden,a scientist at McMaster University in Hamilton,Ontario,heard about a crime in
which the suspect bled onto a cell phone and later dropped the______________(57).This made her wonder
whether traces of DNA lingered on cell phones even when no blood was involved.______________(58)she and
colleague Margaret Wallace of the City University of New York analyzed the flip-open phones of 10 volun-
teers.They used swabs to collect______________(59)traces of the users from two parts of the phone:the
outside,where the user holds it,and the______________(60),which is placed at the user's ear.
The scientists scrubbed the phones using a solution made mostly______________(61)alcohol.The aim of
washing was to remove all detectable traces of DNA.The owners got their phones______________(62)for
another week.Then the researchers collected the phones and repeated the swabbing of each phone once
more.
The scientists discovered DNA that _____________(63)to the phone's speaker on each of the phones.
Better samples were collected from the outside of each phone,but those swabs also picked up DNA that be-
longed to other people who had apparently also handled the phone.______________(64),DNA showed up even
in swabs that were taken immediately after the phones were scrubbed.That suggests that washing won't remove
all traces of evidence from a criminal's device.So cell phones can now be added to the
______________(65)of clues
that can clinch a crime-scene investigation.
_________(65)
A:explanation
B:discovery
C:book
D:list
My friend's reply was courteous but firm.
A:efficient
B:respectable
C:well-informed
D:respectful
查看答案
A:efficient
B:respectable
C:well-informed
D:respectful
共用题干
The Greatest Mystery of Wha1eg
The whale is a warm一blooded,air-breathing animal,giving birth to its young alive,sucking them一and,
like all mammals,originated on land. There are many__________(51)of this. Its front flippers (鳍状肢）,
used for steering and stability,are traces of feet.
Immense strength is________(52)into the great body of the big whales,and in fact most of a
whale',body is one gigantic muscle.The blue whale'S pulling strength has been estimated________.(53)
400 horsepower. One specimen was reported to have towed（拖）。whaling vessel for seven hours at the
_______(54)of eight knot（节）.
An angry whale will________(55).A famous example of this was the fate of Whaler Essex,
________(56)was sunk off the coast of South America early in the last century.More recently,steel ships
have_(57)their plates buckled（使弯曲）in the same way. Sperm whales（抹香鲸）were known
to seize the old-time whaleboats in their jaws and crush them.
The greatest________(58)of whales is their diving ability.The sperm whale dives to the bottom for
his________(59)food,the octopus（章鱼）,In that search he is known to go as far down as 3 , 200 feet,
where the________(60)is 1,400 pounds,to a square inch.Doing so he will________(61)underwa-
ter as long as one hour. Two special skills are involved in this storing up enough________(62)(all
whales are air-breathed)and tolerating the great change in pressure.Just how he does it scientists have not
_________(63).It is believed that some of the oxygen is stored in a special________(64)of blood
vessels,rather than just held in the lungs.And it is believed that a special kind of oil in his head is some sort
of a compensating mechanism that_________(65)adjusts the internal pressure of his body.But since you
can't bring a live whale into the laboratory for study,no one knows just how these things work.
_________(55)
A:abandon
B:attack
C:leave
D:board
查看答案
The Greatest Mystery of Wha1eg
The whale is a warm一blooded,air-breathing animal,giving birth to its young alive,sucking them一and,
like all mammals,originated on land. There are many__________(51)of this. Its front flippers (鳍状肢）,
used for steering and stability,are traces of feet.
Immense strength is________(52)into the great body of the big whales,and in fact most of a
whale',body is one gigantic muscle.The blue whale'S pulling strength has been estimated________.(53)
400 horsepower. One specimen was reported to have towed（拖）。whaling vessel for seven hours at the
_______(54)of eight knot（节）.
An angry whale will________(55).A famous example of this was the fate of Whaler Essex,
________(56)was sunk off the coast of South America early in the last century.More recently,steel ships
have_(57)their plates buckled（使弯曲）in the same way. Sperm whales（抹香鲸）were known
to seize the old-time whaleboats in their jaws and crush them.
The greatest________(58)of whales is their diving ability.The sperm whale dives to the bottom for
his________(59)food,the octopus（章鱼）,In that search he is known to go as far down as 3 , 200 feet,
where the________(60)is 1,400 pounds,to a square inch.Doing so he will________(61)underwa-
ter as long as one hour. Two special skills are involved in this storing up enough________(62)(all
whales are air-breathed)and tolerating the great change in pressure.Just how he does it scientists have not
_________(63).It is believed that some of the oxygen is stored in a special________(64)of blood
vessels,rather than just held in the lungs.And it is believed that a special kind of oil in his head is some sort
of a compensating mechanism that_________(65)adjusts the internal pressure of his body.But since you
can't bring a live whale into the laboratory for study,no one knows just how these things work.
_________(55)
A:abandon
B:attack
C:leave
D:board
共用题干
Electromagnetic Energy
1 White light seems to be a combination of all colors.The energy that comes from a source of light is not limited to the kind of energy you can see.Heat is given off by a flame or an electric light.On a cloudy day it is possible to get a sunburn even though you feel cool.Visible light and the kinds of energy that produce warmth and sunburn are examples of electromagnetic energy.
2 The sun is 93 million miles from the earth.Yet we can use energy from the sun because electromagnetic energy travels through space.
3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signals travel from transmitters to receivers as low-energy electromagnetic waves.Infrared（红外线的）radiation is an electromagnetic wave.When it is absorbed by matter,heat is produced.Waves of infrared and visible light have more energy than waves of radio,television,or radar.Ultraviolet rays（紫外线）and X-rays are electromagnetic waves with even greater amounts of energy.Infrared radiation is used in cooking food and heating buildings. Sunlight and electric lights are part of our requirements for normal living.Ultraviolet radiation is useful in killing certain disease organisms.X-rays and gamma rays have so much energy that they travel through solid objects. They can be used to detect and treat cancer.X-rays are used in industry to find hidden cracks in metal,and in medicine to reveal broken bones.
4 Usually we use electricity to generate electromagnetic energy.The source of most of our energy is the sun.Heat from the sun causes water to evaporate.When the water falls to the earth as rain,some of it is trapped behind dams and then used to operate electric generators.Other generators are powered by coal,but the energy stored in coal came from the sun,too.
5 Until recently,the source of the tremendous amount of energy given off by the sun was a puzzle.If the sun depended on chemical reactions,it would have used up all its energy long ago.Experiments with electromagnetic radiation led to the theory that mass can be converted into energy.About forty years after the theory was proposed , nuclear energy was harnessed（利用）by man.Chemical energy comes from electron （电子）rearrangement.Nuclear energy comes from a change in the nucleus of an atom.Compared with chemical reactions,nuclear reactions release millions of times more energy per pound of fuel.We now believe that the sun's energy comes from the nuclear reactions in which hydrogen is changed into helium（氦）.
6 Nuclear energy is beginning to compete with coal as an economical source of'power to generate electricity.It is also being used to operate engines in large ships.Scientists continue to seek new and better methods of obtaining and using energy.
X-rays and gamma rays can be used to detect and treat cancer______.
A:when it is absorbed by matter
B:when it is cloudy
C:because they can pass through solid objects
D:when the sunrays are fierce.
E:when a change in the nucleus of an atom takes place
F:when electron rearrangement takes place
查看答案
Electromagnetic Energy
1 White light seems to be a combination of all colors.The energy that comes from a source of light is not limited to the kind of energy you can see.Heat is given off by a flame or an electric light.On a cloudy day it is possible to get a sunburn even though you feel cool.Visible light and the kinds of energy that produce warmth and sunburn are examples of electromagnetic energy.
2 The sun is 93 million miles from the earth.Yet we can use energy from the sun because electromagnetic energy travels through space.
3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signals travel from transmitters to receivers as low-energy electromagnetic waves.Infrared（红外线的）radiation is an electromagnetic wave.When it is absorbed by matter,heat is produced.Waves of infrared and visible light have more energy than waves of radio,television,or radar.Ultraviolet rays（紫外线）and X-rays are electromagnetic waves with even greater amounts of energy.Infrared radiation is used in cooking food and heating buildings. Sunlight and electric lights are part of our requirements for normal living.Ultraviolet radiation is useful in killing certain disease organisms.X-rays and gamma rays have so much energy that they travel through solid objects. They can be used to detect and treat cancer.X-rays are used in industry to find hidden cracks in metal,and in medicine to reveal broken bones.
4 Usually we use electricity to generate electromagnetic energy.The source of most of our energy is the sun.Heat from the sun causes water to evaporate.When the water falls to the earth as rain,some of it is trapped behind dams and then used to operate electric generators.Other generators are powered by coal,but the energy stored in coal came from the sun,too.
5 Until recently,the source of the tremendous amount of energy given off by the sun was a puzzle.If the sun depended on chemical reactions,it would have used up all its energy long ago.Experiments with electromagnetic radiation led to the theory that mass can be converted into energy.About forty years after the theory was proposed , nuclear energy was harnessed（利用）by man.Chemical energy comes from electron （电子）rearrangement.Nuclear energy comes from a change in the nucleus of an atom.Compared with chemical reactions,nuclear reactions release millions of times more energy per pound of fuel.We now believe that the sun's energy comes from the nuclear reactions in which hydrogen is changed into helium（氦）.
6 Nuclear energy is beginning to compete with coal as an economical source of'power to generate electricity.It is also being used to operate engines in large ships.Scientists continue to seek new and better methods of obtaining and using energy.
X-rays and gamma rays can be used to detect and treat cancer______.
A:when it is absorbed by matter
B:when it is cloudy
C:because they can pass through solid objects
D:when the sunrays are fierce.
E:when a change in the nucleus of an atom takes place
F:when electron rearrangement takes place
共用题干
Learn About Light
1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso-
phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what
we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag
like a wave.According to them,light spread out and travelled like a straight line.This theory was accepted
during the 19th century.
2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the
photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to
are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree
that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to
see things around us.
3 Things that give off light are known as sources of light.During the day,the primary source of light is
the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass
tube.
4 When we draw the way light travels we always use straight lines.This is because normally light rays
travel in a straight line.However,there are some instances that can change the path and even the nature of
light. They are reflection,absorption,interference（干扰）,etc.
5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte
Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed
a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,
number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313
million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per
second.This is about a million times faster than the speed of an airplane.
Stars,flames,flashlights are some examples of_______.
A:sources of light
B:the speed of light
C:the path of light
D:a straight line
E:a beam of light
F:a form of energy
查看答案
Learn About Light
1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso-
phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what
we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag
like a wave.According to them,light spread out and travelled like a straight line.This theory was accepted
during the 19th century.
2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the
photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to
are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree
that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to
see things around us.
3 Things that give off light are known as sources of light.During the day,the primary source of light is
the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass
tube.
4 When we draw the way light travels we always use straight lines.This is because normally light rays
travel in a straight line.However,there are some instances that can change the path and even the nature of
light. They are reflection,absorption,interference（干扰）,etc.
5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte
Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed
a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,
number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313
million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per
second.This is about a million times faster than the speed of an airplane.
Stars,flames,flashlights are some examples of_______.
A:sources of light
B:the speed of light
C:the path of light
D:a straight line
E:a beam of light
F:a form of energy