题目内容
（请给出正确答案）
A.makes enough narrow focus
B.is made enough narrow to focus
C.can be made narrow enough to focus
D.may be made enough narrow to focus
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更多“A laser beam ________ on a sin…”相关的问题
A．only in the areas of construction
B．to cure a patient of a disease
C．in a few areas because it’s not so powerful
D．to do whatever people want to
It's similar to an ordinary record，except that it's read by a laser beam，and the information recorded on the aluminium is digital.
The makers claim that a CD can reproduce the original sound perfectly，without any distortion or background hiss. As the system is computerized，there's no loss of quality between the studio master and the record you buy.
Also，a CD is much tougher-than a vinyl(乙烯基)record，so it doesn't need such careful handling. Dust and dirt won't damage it，and as there's no contact between the laser and the disc, it will never wear out.
Part A
Directions: Read the following three texts. Answer the questions on each text by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1.
In recent years scientists have found that the laser has a wide variety of applications, making it one of the most important inventions for improving our quality of life.
One important field in which the laser has many applications is communications. Scientists have found that the laser beam can transmit human voices; as a result, telephone companies are now using laser light signals to transmit telephone calls through extremely small cables that are capable of carrying many more transmissions than the standard telephone cables. An additional advantage is that these systems using the laser light signals are also able to transmit video telephone conversations.
Another, perhaps less-known, field in which lasers are helping improve the quality of life is metrology—the science of measurement. The extremely straight, narrow laser beam can be used to put the parts of a structure being built into the correct position to each other. The laser beam has also been used to measure remote distances, for example, the precise distance from the Earth to the Moon. And finally, the laser can be used to measure the drifts of the Earth's plates. This measurement, along with other data, can help in the pre-diction of the earthquakes.
Probably the most vital application of the laser is in the field of medicine. Scientists have developed a laser kniffe that surgeons can use for operations. These knives are now used widely because they cut sharply and because the beam seals off the blood vessels that it cuts, thus reducing blood loss considerably.
When Dr. Theodore got the first laser to work in July 1960, what uses it would have were unknown; in fact he called it a multimillion-dollar "solution in search of a problem". As we have seen, the uses of the laser are numerous. It is being used in the fields of medicine, communications, and metrology. There are many, many more applications, such as in the areas of defense and space travel. What should be apparent by now is that there are many problems the laser is helping to solve, and that the laser, if used wisely, can be a life-saving device.
According to the text, the laser can______.
A．standardize telephone cables
B．remove communications jams
C．improve the quality of human voices
D．increase the capacity of communications
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
The first innovation in the design of combat binoculars(双筒望远镜)in over 200 years is on the horizon. The device, called "talking binoculars", is derived from the strategic satellite-to-satellite communications program. The idea is to use one pair of binoculars to project a laser beam to carry a scout's' observations to a second pair as the receiver.
Military scouts today cannot use radios during radio silent scouting missions inside enemy territory because the enemy can detect and locate their transmissions. With the new "talking" binoculars, when a forward military scout sees the enemy through transmitting laser binoculars and depresses the target locate and store button, global positioning system technology will measure the enemy's target position. Then, the binoculars store the information and use its invisible laser beam to transmit the enemy's position to a receiving set of binoculars. The receiving scout can then immediately transmit target data back to the lines. The military scout will no longer need maps, have to depend on written notes, or leave a position to report back to the commander.
The innovative binoculars also solve the aged-data problem by relaying the military scout's observations in near-real time to the commander in the tactical(战术的) operations center. The scout does not need to personally return to lines to make a report which is aged by the time the commander receives it.
"Enemy detection of the binoculars is near impossible because the weak laser beam is projected from point to point," Strickland said. "An enemy searching for a weak' laser source requires sensitive optical detectors and must be near the receiver to detect the weak laser. It will be much easier for the scout to see the enemy than for the enemy to detect the laser beam. By comparison, radio broadcast is transmitted in all directions, allowing easy detection by a prepared enemy from all angles." he said.
Digital laser communications is a valuable technology. Its advantage stems from providing high data rate communications capability when the mission prevents scouts from using their radios. A weak laser beam can carry digitized voice messages, targeting data and high-quality video images at extremely high data rates.
Military planners are already envisioning a day when all communications on a battlefield, between tanks or between tanks and helicopters, to name only two examples, are transmitted by laser. Theoretically, a laser-based communications system could handle 200,000 voice channels. Currently, even the most powerful high-capacity lasers, capable of transmitting 100 TV channels, weigh only 29 pounds, so they are easily deployed on vehicles or aircraft. In the future, lasers may also transmit information directly from orbiting satellites.
Without the talking binoculars, a scout during radio silent scouting missions ______.
A．can be easily detected and located by the enemy
B．is not able to determine the enemy's target position
C．has to make a record of what he has observed
D．risks getting caught when returning to report back
The code is called the Universal Product Code (UPC). It is designed to add speed and efficiency to stores by using computers. It can do this in several ways. First, it is not necessary for workers to put individual prices on items. Errors in prices are eliminated, or done away with. Also, the time spent checking out is reduced. UPC gives an itemized receipt to the customer with all the items, prices, and totals. The store clerk does not need to spend time checking the price on the item and punching it into cash register. This UPC computerized system will probably save as much as 45 percent of the checkout clerk's time.
What do the stripes mean？ How does the computer interpret the stripes？ The number printed below the vertical bars identifies the manufacturer and the manufacturer's item. As many as 10 trillion individual machinereadable numbers can be used with this system.
Codes are scanned by ______.
A．the checkout clerk
B．the customers themselves.
C．a laser beam of light.
D．the cash register.
Part A
Directions :
Read the following three texts. Answer the questions on each text by choosing A, B, C or D. Mark
your answers on, ANSWER SHEET1.
Text 1
In recent years scientists have found that the laser has a wide variety of applications, making it one of the most important inventions for improving our quality of life.
One important field in which the laser has many applications is communications. Scientists have found that the laser beam can transmit human voices; as a result, telephone companies are now using laser light signals to transmit telephone calls through extremely small cables that are ca-pable of carrying many more transmissions than the standard telephone cables. An additional advan-tage is that these systems using the laser light signals are also able to transmit video telephone con-versations.
Another, perhaps less-known, field in which lasers are helping improve the quality of life is metrology-the science of measurement. The extremely straight, narrow laser beam can be used to put the parts of a structure being built into the correct position to each other. The laser beam has al- so been used to measure remote distances, for example, the precise distance from the Earth to the Moon. And finally, the laser can be used to measure the drifts of the Earth's plates. This measure- ment , along with other data, can help in the prediction of the earthquakes.
Probably the most vital application of the laser is in the field of medicine. Scientists have de-veloped a laser knife that surgeons can use for operations. These knives are now used widely because they cut sharply and because the beam seals off the blood vessels that it cuts, thus reducing blood loss considerably.
When Dr. Theodore got the first laser to work in July 1960, what uses it would have were un- known; in fact he called it a multimillion-dollar " solution in search of a problem". As we have seen, the uses of the laser are numerous. It is being used in the fields of medicine, communica-tions, and metrology. There are many, many more applications, such as in the areas of defense and space travel. What should be apparent by now is that there are many problems the laser is help-ing to solve, and that the laser, if used wisely, can be a life-saving device.
46. According to the text, the laser can_________ .
[ A] standardize telephone cables
[ B ] remove communications jams
[ C] improve the quality of human voices
[ D] increase the capacity of communications
A laser beam can be turned into a ______ weapon.
A．dead
B．deathly
C．dying
D．deadly
A laser beam can be turned into a______ (dead) weapon.
Codes are scanned by ______.
A．the checkout clerk
B．the customers themselves
C．a laser beam of light
D．the cash register
A laser beam can be turned into a ______ weapon.
A) dead B) dying C) deadly D) deathly
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