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1、当转动检偏镜时，观测目镜中视场将出现交替变化的明暗光强，则人眼最敏感的视场为： When the polarizer is rotating, the light and dark light intensity in the field of view will change alternately. The most sensitive field of view of the human eye is
A.三荫板中央石英片对应的面积为暗区，其余部分为亮区，视场特点为中央暗两侧亮。 The area corresponding to the central quartz plate of the three shade board is dark area, and the rest part is bright area. The field of view is dark in the center and bright on both sides#B.三荫板中央石英片分界线消失，亮度均匀且较暗的均匀视场。 The dividing line of quartz plate in the center of the three shade board disappears, and the field of view is dark with uniform brightness .#C.三荫板中央石英片对应的面积为亮区，其余部分为暗区，视场特点为中央参考答案和解析
B
更多 “1、当转动检偏镜时，观测目镜中视场将出现交替变化的明暗光强，则人眼最敏感的视场为： When the polarizer is rotating, the light and dark light intensity in the field of view will change alternately. The most sensitive field of view of the human eye isA.三荫板中央石英片对应的面积为暗区，其余部分为亮区，视场特点为中央暗两侧亮。 The area corresponding to the central quartz plate of the three shade board is dark area, and the rest part is bright area. The field of view is dark in the center and bright on both sides#B.三荫板中央石英片分界线消失，亮度均匀且较暗的均匀视场。 The dividing line of quartz plate in the center of the three shade board disappears, and the field of view is dark with uniform brightness .#C.三荫板中央石英片对应的面积为亮区，其余部分为暗区，视场特点为中央” 相关考题
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CIn most situations, light helps us see. But nowadays humans are using too much of it so that it is in fact a kind of pollution.When it comes to looking at the night sky, too much light makes it difficult for us to watch some of life’s most wonderful sights: stars, planets and even galaxies(星系).According to scientific research, about 2, 500 stars can be seen by the human eye without using any special equipment(设备). But because of light pollution, you can only see 200 to 300 stars from today’s countryside, and no more than ten stars from a city. In most big cities, people cannot see the sky filled with stars like they did in their childhood.Light pollution affects more than just our view of sky. Research shows that lots of nighttime light can harm wildlife, too.When birds fly to another place over cities, they sometimes get lost by the brightness and fly in circles(圈) until they drop from tiredness. Sea turtles(海龟) need dark beaches for laying eggs, but they can’t find their ideal places because of those bright lights.Too much light at night may even affect human health, but scientists are not sure of that. They are still learning more.In order to prevent things from going worse, governments and some organizations are working to reduce light pollution. Many cities and towns have taken action to reduce the use of lights at night. Lights are used only when and where they are truly needed. They also shine lights down at the ground instead of up into the sky and use lower brightness levels.Hopefully, in the near future, humans can enjoy the clear and beautiful sky again and all the wildlife will live a peaceful and undisturbed life, too.27. Why does the writer think that too much light is a kind of pollution?A. Because there are fewer and fewer stars.B. Because human health has been affected.C. Because too much light is a waste of energy.D. Because some of the wildlife can be harmed.
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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
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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.Paragraph 5______A: How Is the Nature of Light Explained Today?B: What Are Sources of Light?C: How Did Physicists Measure the Speed of Light?D: How Does Light Travel?E: How Did People Think of Light Years Ago?F: What Causes a Shadow?
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Light rays are turned aside by the intense gravitational field surrounding a black hole.A:heightened
B:deflected
C:rotated
D:created
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Solar Power Without Solar CellsA dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.The researchers found a way to make an"optical________(51)",said Stephen Rand,a professor in the departments of Electrical Engineering and Computer Science,Physics and Applied Physics.Light has electric and magnetic_______(52).Until now,scientists thought the effects of the mag-netic field were so weak that they could be________(53).What Rand and his colleagues found is that at the right intensity,when light is traveling through a material that does not_________(54)electricity,the light field can generate magnetic effects that are 100 million times stronger than previously expected.Under these circumstances,the magnetic effects develop strength_________(55)to a strong electric effect."This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation,"Rand said."In solar cells,the_________(56)goes into a matenal,gets absorbed and creates heat.Here,we expect to have a very low heat load.Instead of the light being absorbed,energy is stored in the magnetic moment.Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power________(57)."What makes this possible is a previously unde- tected brand of"optical rectification",says William Fisher,a doctoral student in applied physics.In tradi- tional optical rectification,light's electric field causes a charge separation,or a pulling_________(58)of the positive and negative charges in a material.This sets up a voltage,similar to______(59)in a battery.Rand and Fisher found that under the right circumstances and in right types of materials,the light's magnetic field can also create optical rectification.The light must be shone through a________(60)that does not conduct electricity,such as glass.And it must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn't this_______(61)on its own,but new materials are being sought that would work at lower intensities,Fisher said."In our most recent paper,we show that incoherent light like sunlight is theoretically almost _________(62)effective in producing charge separation as laser light is,"Fisher said.This new_________(63)could make solar power cheaper,the researchers say.They predict that with improved materials they could achieve 10 percent efficiency in converting solar power to usable energy.That's equivalent to today's commercial-grade solar cells."To manufacture modern solar cells,you have to do. _______(64)semiconductor processing,"Fisher said."All we would need are lenses to focus the light and a fiber to guide it.Glassworks for _________ (65).It's already made in bulk,and it doesn't require as much processing.Transparent ceramics might be even better."_________(60)A:materialB:deviceC:detectorD:meter
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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.Some instances such as reflection and absorption can change______.A: sources of lightB: the speed of lightC: the path of lightD: a straight lineE: a beam of lightF: a form of energy
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What is the most important feature of the backpack invented by Lawrence C.Rome and his colleagues?A It produces electricity for electronic devices while the wearer walks.
B It can be used as cellphones，GPS in the military actions or field studies.
C It is small and convenient.
D It is light and easy to carry.
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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
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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.Some instances such as reflection and absorption can change_________. A:sources of lightB:the speed of light C:the path of lightD:a straight lineE:a beam of lightF:a form of energy
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This cargo light is not （）enough. Please change it for a new one.A、lightB、brightC、tightD、dark
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Field of view( FOV) relates to the ( )A、diameter of the patient apenure of the imagerB、maximum diameter of the patientC、diameter of the area that isreconstructedD、the diameter of a pixel
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tommy has created a sales view in his sales.nsf database. Tommy wants negative numbers in the sales number column in the view parenthesis. which one of the following should tommy do?（）A、select the parenthesis when negative value in the view properties box B、select the parenthesis when negative value in the column properties box C、use the @function @negative to set this in the column formula in the view D、use a formula to format the value in the field on the form that will be displaying in the view
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when eduar tried open the coming attractions view. he got the following error message: incorrect data type for operator or @function: text expected. What did he do to cause this to happen?（）A、entered text in a number fieldB、neglected to place a formula in a validation eventC、neglected to place a formula in a translation eventD、combined a text field and a time field in formula
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jim has created a field hint for the address field. Users tell him this text disappears when they click in the address field. which one of the following is most likely reason?（）A、 the address field is computed B、 jim should have used a text popup C、 jim stored the field hint in the database D、 field hint only display when the user has not clicked in the field （field hint）
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单选题How is the intensity of a light expressed in the Light Lists?（）.A
Luminous rangeB
Geographic rangeC
Nominal rangeD
Meteorological range
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单选题jim has created a field hint for the address field. Users tell him this text disappears when they click in the address field. which one of the following is most likely reason?（）A
the address field is computed B
jim should have used a text popup C
jim stored the field hint in the database D
field hint only display when the user has not clicked in the field （field hint）
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单选题From your position you observe a rotating white and green light to the north. This light is most likely（）.A
from a submarine on the surfaceB
the light at Southeast PointC
at an airportD
on a coastal patrol vessel
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单选题Field of view( FOV) relates to the ( )A
diameter of the patient apenure of the imagerB
maximum diameter of the patientC
diameter of the area that isreconstructedD
the diameter of a pixel
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单选题The most common type of AC service generator found aboard ship is the stationary （）.A
electromagnetic field, revolving armature typeB
electromagnetic field, oscillatory armature typeC
armature, oscillatory electromagnet field typeD
armature, rotating electromagnetic field type
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单选题Which frame field do error detection schemes view to perform their function?（）A
ERRB
FlagC
FCSD
MTUE
MACF
PDU
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单选题When making landfall at night，you can determine if a light is a major light or an offshore buoy by（）.A
the intensity of the lightB
checking the period and characteristics against the Light ListC
the color，because the buoy will have only a red or a green lightD
Any of the above can be used to identify the light
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单选题From your position you observe a rotating white and green light to the north. This light is most likely（）.A
at an airportB
on a naval mine-countermeasures vesselC
Block Island North LightD
on a vessel engaged in public safety activity
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