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[阅读小分队] 揽瓜阁阅读做题小分队 第105天 LCD's and LED's

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发表于 2021-7-13 01:17:37 | 显示全部楼层 |阅读模式
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Despite their acronymic similarity, LEDs and LCDs represent distinct display technologies. In LEDs, or light-emitting diodes, two different semiconductor materials are layered together: n-type, in which mobile electrons carry negative charge, and p-type, in which “holes” in an otherwise bound sea of electrons carry positive charge. When electric current flows through the p-n junction between layers, an n-type electron falling into a p-type hole releases a photon, a specifically colored particle of light.

The dominant technology currently used in most consumer product displays is the active matrix liquid crystal diode display (LCD). LCDs apply thin-film transistors (TFTs) of amorphous silicon sandwiched between two glass plates. The TFTs supply voltage to liquid-crystal-filled cells, or pixels, between the sheets of glass. Liquid crystals can twist the polarization, or wave orientation, of light. Just as a guitar string can vibrate sideways or up and down, so a light wave can be polarized horizontally or vertically. Polarizing filters act as selective gates, transmitting light polarized one way but not the other. Within a pixel, liquid crystals in their relaxed, coiled state rotate the polarization of ambient light enough to make surrounding filters transparent. Alternatively, applied electrical signals uncoil the crystals, causing the filters to block light and the pixel to become opaque. LCDs that are capable of producing color images, such as in televisions and computers, reproduce colors by blocking out particular color wavelengths from the spectrum of white light until only the desired color remains. The variation of the intensity of light permitted to pass through the matrix of liquid crystals enables LCD displays to present images full of gradations of different colors.

The amount of power required to untwist the crystals to display images is much lower than that required for analogous processes using other technologies, such as plasma. The dense array of crystals displays images from computer sources extremely well, with full color detail, no flicker, and no screen burn-in. Moreover, the number of pixels per square inch on an LCD is typically higher than that for other display technologies; LCD monitors are excellent at displaying large amounts of data with exceptional clarity and precision.


1. According to the passage, the application of an electrical signal or current to both an LED and an LCD pixel results in which of the following?
A. Both the LED and the LCD pixel become bright.
B. The LED becomes dark, but the LCD pixel transmits light
C. The LED becomes bright, but the LCD pixel ceases to transmit light.
D. The LED becomes dark, but the liquid crystals in the pixel uncoil.
E. The LED becomes bright, but the liquid crystals in the pixel coil up.


2. The author most likely mentions “plasma” in the third paragraph in order to
A. provide an example of a technology that operates differently than LCDs
B. reinforce the importance of the commercial development of LCDs
C. describe the contrasting workings of another technology
D. indicate the greater number of applications for LCDs
E. explain the features of a competing type of display


3. The process through which an LCD monitor displays different colors is most closely analogous to
A. the partial blocking of an hourglass so that a limited stream of grains of sand fall into the lower portion
B. the use of rigid sizing boxes at an airport security checkpoint in order to allow the passage of certain sizes of luggage while excluding other sizes of luggage
C. the soundproofing of a recording studio so that any performances within are muted to those outside
D. the cutting out of characters from a sheet of paper so that a lamp in front of the paper casts shadows in the shapes of the characters
E. the emission of warmer air by an air vent on the outside of a building while an air conditioning system cools the interior of the building


4. Which of the following can be inferred about uncoiled liquid crystals in an LCD pixel?
A. Electric currents cause them to release photons.
B. They are in a relaxed state, in comparison to their high-energy coiled state.
C. They are found in one of two wave orientations, horizontal or vertical.
D. They fail to rotate the polarization of surrounding photons enough to allow them to pass through nearby filters.
E. They cause the pixel to become transparent.

5.In this passage, the author is primarily concerned with
A. delineating the commonalities between two seemingly divergent phenomena
B. contrasting the uses of electrical power for two contrary purposes
C. explicating the scientific underpinnings of two dissimilar technologies
D. describing the economic significance of two processes
E. analyzing the relationship between two methods of displaying information


参考答案:
CABDC

发表于 2021-7-13 08:56:12 | 显示全部楼层
Caccc
发表于 2021-7-13 10:36:15 发自 iPhone | 显示全部楼层
CBADE
发表于 2021-7-13 11:14:34 | 显示全部楼层
1 E
2 B
3 B
4 C
5 C
发表于 2021-7-13 12:12:05 | 显示全部楼层
CABDC
第一段总起LED与LCD代表了不同的显示技术,并具体介绍了LED的工作原理:
1.    LED中,两种半导体材料are layered together:n-type和p-type
2.    N-type里有负电荷,P-type里有正电荷
3.    通电时,正负电荷接触释放光子photon

第二段主要介绍LCD的工作原理:
1.    TFTs在两层玻璃之间,并为处于两层玻璃间的pixel提供电压
2.    Pixel中的液晶可以改变光的波向or polarization,举例吉他
3.    Polarizing fliter挑选光波
4.    在一个pixel中,处于relaxed,coiled 状态的液晶makefliters透明;通电后液晶uncoil,导致filtersblock light以及pixel不透明
总结:
A. LCD通过block out particular color 留下desired color来display color images,举例应用在电视和计算机中

B. 通过液晶矩阵的光的强度变化导致LCD可以展示不同颜色的图像

第三段讲LCD的优势
1.    LCD与plasma相比所需的power更少
2.    Display images from computer sourceswell:full color,no flicker andno screen burn-in
3.    Be excellent at displayinglarge amounts of data


发表于 2021-7-13 13:04:05 | 显示全部楼层
BBBCC
发表于 2021-7-13 14:44:41 | 显示全部楼层
用时超了9分钟(反省)
第一段说LED和LCD不同,简介了LED工作原理。
第二段开始介绍LCD,说它占领主科技地位,解释了LCD的运作原理。
第三段进一步说了LCD的优点。

答案:CABDC
第一个问题:对LED和LCD像素作用一个电信号或电流,它们的结果会怎样?(细节题,需要回文中找)
对于LED,在文中第一段最后一句:当电流在层与层间流过p-n结点时,一个n型电子会落入到p型穴中释放出一个光子,这是一个特殊颜色的光粒子。
所以LED会变亮,即bright。
对于LCD像素,在文中第二段讲它的运作原理说到LCD像素会停止透光只让想要的颜色透过保存下来。
选C

第二题问作者提到plasma的作用,在文中第三段,作者提到plasma与LCD的运作原理不同,最后一句衬托出LCD的优点。
选A

第三题:和LCD显示器显示不同颜色最接近的比喻是:
文中第二段说LCDs that are capable of producing color images, such as in televisions and computers, reproduce colors by blocking out particular color wavelengths from the spectrum of white light until only the desired color remains.
和选项B的机场安检原理最像。

第四题:由在LCD像素中展开的液晶可以推理出什么?
在文中第二段:Within a pixel, liquid crystals in their relaxed, coiled state rotate the polarization of ambient light enough to make surrounding filters transparent.
注意,文中这句话说的是coiled 的情况是enough to make....,而问题问的是uncoiled情况,所以正好相反,是答案D,fail to...enough to ...

第五题:作者在文中的主旨:
显然,作者介绍了LED和LCD的不同运作原理,所以选C,解释了两个不同技术运作原理的科学基础。

发表于 2021-7-13 14:58:14 | 显示全部楼层
时间:11分半
1.文章
第一段讲LED的原理
第二段讲LCD的原理
第三段吐出LCD的优势
2.
EBBDC
发表于 2021-7-13 17:44:51 | 显示全部楼层
Mark一下!               
发表于 2021-7-13 19:04:37 | 显示全部楼层
Mark一下!               
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