单选题A camera takes light rays bounced off objects and _____ them on a sheet of a film.AconcentratesBmixesCcombinesDfocuses
单选题
A camera takes light rays bounced off objects and _____ them on a sheet of a film.
A
concentrates
B
mixes
C
combines
D
focuses
参考解析
解析：
句意：照相机吸收物体反射回来的光线，再把它们聚焦在胶片上。focus意为“使集中在焦点上，调焦距”。concentrate意为“集中，聚集”；mix意为“混淆，混合”；combine意为“联合，结合”。
句意：照相机吸收物体反射回来的光线，再把它们聚焦在胶片上。focus意为“使集中在焦点上，调焦距”。concentrate意为“集中，聚集”；mix意为“混淆，混合”；combine意为“联合，结合”。
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共用题干Electromagnetic Energy1 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.Infrared radiation can produce heat______. A:when it is absorbed by matterB:when it is cloudyC:because they can pass through solid objectsD:when the sunrays are fierce.E:when a change in the nucleus of an atom takes placeF:when electron rearrangement takes place
共用题干Electromagnetic Energy1 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 matterB:when it is cloudyC:because they can pass through solid objectsD:when the sunrays are fierce.E:when a change in the nucleus of an atom takes placeF:when electron rearrangement takes place
Light rays are turned aside by the intense gravitational field surrounding a black hole.A:heightenedB:deflectedC:rotatedD:created
共用题干Learn about Light1 .Ancient civilizations were amazed by the existence of light for thousands of years. The Greek philosophers 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 was 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 re-ferred 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,flashlights,street lamps and glowing gases in glass tube.4 .When we draw the way light travels we always use straight lines. This is because nor-mally 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.Objects are visible to the human eye as light is______.A: sources of lightB: the speed of lightC: the path of lightD: a straight lineE: a beam of lightF: a form of energy
共用题干第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.Which of the following statements about asteroids is NOT true? A:The WISE telescope can catch and take pictures of them.B:They do not reflect light that reaches them.C:They float through space giving off visible light.D:They are invisible to ordinary cameras.
共用题干第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.It can be inferred from the last paragraph that brown dwarfs__________.A:give off infrared radiationB:are power stars like the sunC:become massive and activeD:are invisible to the WISE telescope
共用题干第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.It is true that infrared radiation_________.A:is not detectable to humansB:looks brighter than visible lightC:is visible light reflected off an objectD:has longer waves than those of visible light
共用题干第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.The camera on WISE_________.A:is equipped with expensive computersB:produces images of objects giving off infrared radiationC:reflects light visible to the human eyesD:is similar to an ordinary digital camera
共用题干第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.What is so special about WISE?A:It is as small as a trashcan.B:It is small in size but carries a large camera.C:Its digital camera can help astronomers to see the unknown space.D:Never before has a telescope carried a digital camera in space.
共用题干Electromagnetic Energy1 White light seems to be a combination of all colors.The energy that comes from a source of light isnot 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 kind of energy that produce warmth and sunburn are examples of electromagnetic energy.2 The sun is 93 million miles away from the earth.Yct we can use energy from die sun because elec-tromagnetic energy travels through space.3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signais 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.Wayes of infrared and visible light have more energy than waves of radio,television,or radar. Ultraviolet rays（紫外线）and X-rays are eleetro-magnetic 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 right through solid objects.They can be used to detect and treat cancer。 X-rays are used in industry to find hiddencracks 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．入bout 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 chemi- cal 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 elec- tricity.It is also being used to operate engines in large ships.Scientists continue to seek new and bettermethods of obtaining and using energy.When electron rearrangement takes place_______________.A:electromagnetic energyB:electromagnetic energy travels through spaceC:came from the sunD:when a change in the nucleus of an atom takes placeE:whlen the sunrays are fierce F:chemical energy is generated
共用题干Electromagnetic Energy1 White light seems to be a combination of all colors.The energy that comes from a source of light isnot 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 kind of energy that produce warmth and sunburn are examples of electromagnetic energy.2 The sun is 93 million miles away from the earth.Yct we can use energy from die sun because elec-tromagnetic energy travels through space.3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signais 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.Wayes of infrared and visible light have more energy than waves of radio,television,or radar. Ultraviolet rays（紫外线）and X-rays are eleetro-magnetic 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 right through solid objects.They can be used to detect and treat cancer。 X-rays are used in industry to find hiddencracks 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．入bout 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 chemi- cal 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 elec- tricity.It is also being used to operate engines in large ships.Scientists continue to seek new and bettermethods of obtaining and using energy.Visible light that produces warmth is an example of _______________.A:electromagnetic energyB:electromagnetic energy travels through spaceC:came from the sunD:when a change in the nucleus of an atom takes placeE:whlen the sunrays are fierce F:chemical energy is generated
共用题干Learn About Light1 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 acceptedduring 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 tosee 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.Objects are visible to the human eye as light is_______. A:sources of lightB:the speed of light C:the path of lightD:a straight lineE:a beam of lightF:a form of energy
Look, 25% off. The $2,500 camera is on sale today. （）A、The camera if of high quality.B、That‘s very kind of you.C、My camera is out of order now.D、Yeah, a surprising bargain. I‘ll buy it.
Which of the following is the process a scanner uses to scan images to a computer？（）A、Light is shown through the image and onto the scanner headB、Light is reflected off a mirror onto the Charged Coupled Device （CCD）C、Light is flashed off a mirror onto the CCDD、Light is reflected off the image and into a camera
单选题Look, 25% off. The $2,500 camera is on sale today. （）AThe camera if of high quality.BThat‘s very kind of you.CMy camera is out of order now.DYeah, a surprising bargain. I‘ll buy it.
单选题The sun gives off light and warmth, that makes it possible for plants to grow.Agives offBthatCitDfor
单选题When summer comes and the light-colored people go to the beaches, ______.Aall of them will tan darklyBfew of them will tan -darklyCmany of them will not tan at allDfew of them will not tan at all
单选题A camera takes light rays bounced off objects and _____ them on a sheet of a film.AconcentratesBmixesCcombinesDfocuses
单选题The luminous range of a light takes into account the（）.Aglare from background lightingBexisting visibility conditionsCelevation of the lightDobserver's height of eye
单选题Which of the following is the process a scanner uses to scan images to a computer？（）ALight is shown through the image and onto the scanner headBLight is reflected off a mirror onto the Charged Coupled Device （CCD）CLight is flashed off a mirror onto the CCDDLight is reflected off the image and into a camera
单选题A light，feathery deposit of ice caused by the sublimation of water vapor directly into the crystalline form，on objects whose temperatures are below freezing，is called（）.AdewBfrostCglazeDsnow