In the past decade, rapid technological progress and a greater demand

Question

In the past decade, rapid technological progress and a greater demand for high-quality digital imaging have led to dramatic advances in video display technology. 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 or polycrystalline silicon sandwiched between two glass plates. The TFTs supply voltage to liquid-crystal-filled cells, or pixels, between the sheets of glass. When hit with an electric charge, the liquid crystals untwist to an exact degree to filter white light generated by a lamp. This filtered light shines directly on the viewing screen or, in the case of projection televisions, is projected through a small chip that acts as a lens. LCDs that are capable of producing color images, such as in televisions and computers, reproduce colors through a process of subtraction, blocking out particular color wavelengths from the spectrum of white light until only the desired color remains. It is the variation of the intensity of light permitted to pass through the matrix of liquid crystals that enables LCD displays to present images full of gradations of different colors.

The nature and functioning of LCD displays present many advantages relative to other display technologies. The amount of power required to untwist the crystals to display images, even dark ones, is much lower than that required for analogous processes using other technologies, such as plasma. The dense array of crystals displays images from computer or other video graphics sources extremely well, with full color detail, no flicker, and no screen burning. Moreover, the number of pixels per square inch on an LCD display is typically higher than that for other display technologies, so LCD monitors are particularly good at displaying large amounts of data with exceptional clarity and precision. As a result, LCD TVs are considered the best display platform for video games, high definition television, movie special effects, and other graphics intensive uses.   1 
 1. The process through which an LCD monitor displays different colors is most closely analogous to

A. An hourglass partially blocked such that a limited stream of grains of sand fall into the lower portion
B. A series of filters that separate all of the components of a mixture according to size
C. A recording studio soundproofed so that any performances within are muted to those outside
D. A piece of construction paper with outlines of characters cut out such that a lamp in front of the paper casts shadows in the shapes of the characters
E. An air vent that emits warmer air outside of a building while an air conditioning system cools the interior of the building

2 
 2. It can be inferred from the passage that an LCD monitor would utilize the most electrical power when displaying

A. a movie scene of a NASCAR race with many computergenerated special effects
B. the introduction sequence for a World War II video game
C. a bright daytime television broadcast of a parade
D. a photorealistic screen saver of a bouquet of flowers
E. a filmed scene set inside a cave with minimal lighting

3 
 3. The passage indicates that each of the following may be considered an advantage of LCD displays relative to other display technologies EXCEPT

A. they consume less power
B. they generally have more pixels per square inch of the display
C. they are able to display continuous video graphics images with no interruption
D. they reflect a widely adopted standard
E. they represent the latest, most advanced technology

4 
 4. The tone of the passage could best be described as

A. supportive advocacy
B. historical discussion
C. objective explanation
D. intellectual exploration
E. qualified support

gmat1393 · Accepted Answer

OFFICIAL EXPLANATION  for Question 4.

This is a general question that asks about the tone of the passage. In order to answer this question, it is useful to briefly examine and summarize the respective paragraphs.

Paragraph 1: LCDs have become the dominant display technology in the past decade.

Paragraph 2: LCDs function by channeling electricity to untwist crystals to block light in order to form colors.

Paragraph 3: LCDs present advantages relative to other display technologies, particularly for certain uses.

The correct answer will effectively identify the tone adopted in these paragraphs.

(A) It is too strong to categorize the author's tone as "advocacy," as the first two paragraphs are purely explanatory. The third paragraph, though listing advantages of LCD displays, does not advocate their use.

(B) Although the first paragraph does mention the time frame and context of the development of LCD displays, neither the second nor third paragraph could be classified as part of a historical discussion, and no contrast is drawn. Thus, it would be inaccurate to characterize the tone of the passage as that of a historical discussion.

(C) CORRECT.  The passage objectively explains the background, functioning, and advantages of LCD displays.

(D) The passage does not indicate any questioning, skepticism, or exploration in its text, and is more technical than intellectual in tone.

(E) Although one could argue that the passage implicitly approves of the development of this new technology, the passage does not advocate for a particular point of view, and there is no evidence of any qualification in its explanation of the functioning and advantages of LCD displays.

gmat1393 · Answer

OFFICIAL EXPLANATION  for Question 3.

This is a specific question that asks us which answer choice is not indicated in the passage as an advantage of LCD displays relative to other display technologies. In order to answer this question, one must examine each answer choice and determine if it is mentioned in the passage.

(A) The second sentence of the third paragraph reads, “The amount of power required to untwist the crystals to display images, even dark ones, is much lower than that required for analogous processes using other technologies, such as plasma.” The passage indicates that LCD displays consume less power than other display technologies.

(B) The fourth sentence of the third paragraph reads, “Moreover, the number of pixels per square inch on an LCD display is typically higher than that for other display technologies, so LCD monitors are particularly good at displaying large amounts of data with exceptional clarity and precision.” The passage indicates that LCD displays generally have more pixels per square inch.

(C) The third sentence of the third paragraph reads, “The dense array of crystals displays images from computer or other video graphics sources extremely well, with full color detail, no flicker, and no screen burn-in.” The passage indicates that LCD displays can present video graphics images with no flicker or interruption.

(D) The second sentence of the first paragraph reads, “The dominant technology currently used in most consumer product displays is the active matrix liquid crystal diode display (LCD).” The passage indicates that the technology is a widely adopted standard, which would logically have certain advantages (e.g. the technology has been widely tested and is known to work).

(E) CORRECT.  While the passage indicates that LCDs are the result of rapid technological progress in the past decade and the dominant technology currently used, the passage does not indicate that LCDs are the most advanced technology. There may be a more cutting edge technology (e.g. LEDs, or Light Emitting Diodes) available for certain applications. Also, the passage does not cite any specific functional advantage to being the latest and most advanced.

gmat1393 · Answer

OFFICIAL EXPLANATION  for Question 1

This question asks which is most analogous to the process through which an LCD display presents different colors. The fifth and sixth sentences of the second paragraph read, “LCDs that are capable of producing color images, such as in televisions and computers, reproduce colors through a process of subtraction, blocking out particular color wavelengths from the spectrum of white light until only the desired color remains. It is the variation of the intensity of light permitted to pass through the matrix of liquid crystals that enables LCD displays to present images full of gradations of different colors. ”This process of subtraction consists of taking a large number of elements, in this case wavelengths of light, and carefully blocking out certain of them while allowing only certain others to get through. We should look for an answer that mirrors this precise process of subtraction.

(A) This answer choice describes a process that does not result in only certain elements passing through. Each grain of sand is equally capable of falling through the hourglass; in fact, all of it will eventually pass through, although it will happen at a slower rate than it might because it the opening is partially blocked.

(B) A series of filters that separate out all of the elements of a mixture is not analogous to filtering out only certain elements and letting others "pass through" to together create the end result.

(C) A soundproofed recording studio blocks all sound, not only certain elements of it. Hence, this is very different from the process described regarding an LCD display.

(D) CORRECT.  A piece of construction paper with outlines of characters cut out would allow certain spaces of light to pass while blocking others, resulting in are fined mixture that has a certain meaning (e.g. the word, “Apple”). This is closely analogous to the process of subtraction through which LCD displays different colors.

(E) An air vent that expels warm air does not carefully select remaining elements, and all of the elements that pass through are indistinguishable from each other.

gmat1393 · Answer

OFFICIAL EXPLANATION  for Question 2.

The third and fourth sentences of the second paragraph of the passage indicate that, in LCD displays, electricity is used to untwist liquid crystals in order to filter white light from a lamp. Also the second sentence of the third paragraph reads that “the amount of power required to untwist the crystals to display images, even dark ones, is much lower than that required for analogous processes . . . “ As a result, it can be inferred that LCDs require more electricity to produce dark images as opposed to lighter images. The correct answer choice will involve a set of images that have a high degree of darkness, and thus a high level of electricity use.

(A) There is no indication in the passage that LCDs require more electricity to display computer-generated special effects than any other images, or that these special effects are dark images.

(B) There is no indication in the passage that LCDs require more electricity to display video game graphics than any other images, or that these graphics are dark images.

(C) There is no indication in the passage that LCDs require more electricity to display video game graphics than any other images; further, a "bright" image cannot also be dark.

(D) There is no indication in the passage that LCDs require more electricity to display photorealistic images than any other images, or that these images are dark images.

(E) CORRECT.  A filmed scene set inside a cave with minimal lighting would certainly be classified as a dark image, which we can infer will use more electricity than a lighter image.

sakshamchhabra · Answer

1. The process through which an LCD monitor displays different colours is most closely analogous to

Although I love such passages over the ones with historians or scholars who take issue with traditionally accepted interpretations of the historical period, this one turned out to be a pain. However, to answer this question we need to hover once again over the 2nd paragraph.

" LCDs that are capable of producing colour images, such as in televisions and computers, reproduce colours through a process of subtraction, blocking out particular colour wavelengths from the spectrum of white light until only the desired colour remains."

It is really important to understand that the functioning of an LCD is similar to that of a subtraction (i.e blocking out unnecessary and letting pass only the required ones)

D. A piece of construction paper with outlines of characters cut out such that a lamp in front of the paper casts shadows in the shapes of the characters

Option D is the correct choice, although at first glance it might look analogus to working of a projector but lets just say that this choice is right because other choices have bigger problems.

Looking at other option choices:

A. An hourglass partially blocked such that a limited stream of grains of sand fall into the lower portion 
although it does involve subtraction and filtering, but the subtraction is of no use or good, and since all the particles are of similar size and shape so there is no bias among which particles are allowed and which ones are stopped.

B. A series of filters that separate all of the components of a mixture according to size 
This one just simply filters out all the particles, but our agenda is to filter the unwanted ones and let the desired ones pass.

One learning that we can take from this question is that letting quibbles with credit answer lead you to choose a manifestly worse answer is something you should be on guard against.

sakshamchhabra · Answer

4. The tone of the passage could best be described as

A. supportive advocacy
B. historical discussion
C. objective explanation
D. intellectual exploration
E. qualified support

A. supportive advocacy- There is no support B. historical discussion- No discussion of history related to anything C. objective explanation- Correct D. intellectual exploration- Author is not one a trip to explore, just presenting mere facts E. qualified support- Qualified means limited, there is no kind of support whatsoever. all options related to opinions should be dismissed straight away

sakshamchhabra · Answer

Greetings mallya12 , While the experts pour in their comments here are my 2 cents, - The process through which an LCD monitor displays different colours is most closely analogous to In the second paragraph, it is mentioned that " LCDs that are capable of producing colour images, such as in televisions and computers, reproduce colours through a process of subtraction, blocking out particular colour wavelengths from the spectrum of white light until only the desired colour remains." The intent of the highlighted portion is that LCD works by blocking out unwanted colour wavelengths and allowing only the desired ones to pass Option B- A series of filters that separate all of the components of a mixture according to size This one just simply filters out all the particles, but our agenda is to filter the unwanted ones and let the desired ones pass. I'll expand more by giving an example, suppose we have a mixture of sand, gravel, and stones. According to this option, LCD works by simply separating all the 3 components (i.e. LCD simply filters out all the different colour wavelengths and presents to us) according to size but that's not how LCD works, it works by blocking (or subtracting) the unwanted particles (=colour wavelengths) and letting the desired ones to pass. ( "until only the desired colour remains" ) on the other hand, option D might not look the best at first glance, but it actually serves the intended meaning i.e blocking out the non-desired light (=colour wavelengths) and letting only the desired ones to pass. D. A piece of construction paper with outlines of characters cut out such that a lamp in front of the paper casts shadows in the shapes of the characters I would be happy to expand further in case you have any questions. looking forward!

sakshamchhabra · Answer

Greetings  mallya12 ,

I would love to expand more on my explanation.

Let's take another example, Suppose If  I want to cast a shadow of my hand on a wall , I would light a torch whose rays would directly fall on the wall ahead, makes sense?
Now, When I obstruct the light of torch with my hand, a shadow of my hand appears on the wall. How does the shadow of my hand form? The desired scenario (=shadow of my hand on the wall) happens because the unwanted light was blocked  (by my hand)  and the desired light was allowed to pass (=process of subtraction in LCD's).

Let's take a look at what 2nd paragraph said-  " LCDs that are capable of producing colour images, such as in televisions and computers, reproduce colours through a process of subtraction, blocking out particular colour wavelengths from the spectrum of white light until only the desired colour remains."

And lastly, let's take a look at option D- A piece of construction paper with outlines of characters cut out such that a lamp in front of the paper casts shadows in the shapes of the characters.

Now relating the option with the example quoted, Here the construction paper with outlines of characters == my hand in the above example to cast a shadow.

Hope that helps:), in case you have any further queries,  please  let me know I would love to expand more on my explanation

Waddup · Answer

the second sentence of the third paragraph reads that “the amount of power required to untwist the crystals to display images, even dark ones, is much lower"- Does this not mean that the power is not affected by the amount of light it gets, no matter how much darkness/ or light is, the power is lower? This is why I thought E might never be the answer. Please explain what am I thinking wrong here

guddo · Answer

2. It can be inferred from the passage that an LCD monitor would utilize the most electrical power when displaying

The passage says LCDs use voltage to untwist liquid crystals, and these crystals filter white light by blocking parts of it.  So the key issue is how much light must be blocked or filtered , not how exciting or graphics-heavy the image is. A very dark image requires the LCD to block most of the white light, so it would require the most relevant crystal activity under the passage’s logic.

A. a movie scene of a NASCAR race with many computer-generated special effects

Wrong. Special effects may require processing power, but the question is about the power used by the LCD monitor itself.

B. the introduction sequence for a World War II video game

Wrong. A video game may be graphics-intensive, but that does not mean the LCD crystals use the most electrical power.

C. a bright daytime television broadcast of a parade

Wrong. A bright image allows much of the white light to pass through. It does not require as much blocking as a very dark image.

D. a photorealistic screen saver of a bouquet of flowers

Wrong. This may involve many colors and details, but it is not the strongest case for maximum light-blocking.

E. a filmed scene set inside a cave with minimal lighting

Correct. A cave scene with minimal lighting would require the LCD to block most of the white light. Since the passage links LCD power use to the untwisting and filtering action of the crystals, this dark scene would use the most electrical power  under the passage’s stated mechanism .

Answer: (E)

guddo · Answer

I'd say, your mistake is in the comparison.

The sentence does not compare  dark LCD images vs. bright LCD images .

It compares  LCD power use vs. other display technologies , even when the LCD is displaying dark images.

So the sentence means:

LCDs require less power than plasma and similar technologies, even for dark images.

It does not mean:

LCDs use the same power for dark and bright images.

For this question, the test’s intended inference is that dark images require more filtering/blocking of white light, so E is the darkest option and therefore best. That inference is a bit awkward, but your reading of the quoted sentence as “power is unaffected by brightness” goes too far.

In the past decade, rapid technological progress and a greater demand

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In the past decade, rapid technological progress and a greater demand

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