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 burn-in. 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.


Q. 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


D is the correct answer. The explanation to reject B is: 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.

However, according the choice, the series of filters separate according to size. That, to me, does not necessarily mean ALL elements are filtered. Can somebody shed some light on this?

I sure can. Our system tagged this question as not sufficiently discriminating b/c too many people in the "top" scoring buckets (and who are therefore expected to get this one right at higher rates) have been choosing B for the reasons you described. I actually re-wrote this one myself yesterday - I changed some other things, too, but specifically I completely changed answer choice B. So don't worry about it - in fact, feel good that you fall into that category of people who are smart enough to know that this one is a little too close for comfort! :)

It'll probably take a week or two for the new version to clear the review process and get into the database, for anyone else who happens to see it during that time.

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

::wipes sweat profusely::

Thanks a lot Stacey. I do feel good after reading your reply.

someone got it right first time without any confusion. Is that ok?

I think the reason to reject B is that blocking of the larger particles will not have any impact on the end result. The end result for example may be a shape you get from the particles or anything else.

As in D the shape of the paper cut ( blocking out light) will obviously directly affect the shadow.

hope that helps..

You're fine if you got it right, you're fine if you didn't get it right (and, specifically, if you got it wrong by choosing B). Overall, actually, don't rate how you're doing based on this question since it failed our discrimination analysis and will be changed accordingly!

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

The question is still there . I faced it in my first MGMAT .

We've taken this question out of the CAT pool for rehab. Many apologies for the fact that it was still showing up. We're implementing changes to our CAT updating process so that issues such as this one, once identified, do not slip any more through the cracks.