It is currently 11 Dec 2017, 18:06

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Despite their acronymic similarity, LEDs and LCDs represent distinct

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
Joined: 08 Oct 2012
Posts: 10

Kudos [?]: 2 [0], given: 3

Despite their acronymic similarity, LEDs and LCDs represent [#permalink]

Show Tags

New post 07 Dec 2012, 12:12
1
This post was
BOOKMARKED
Question 1
00:00
A
B
C
D
E

Question Stats:

38% (01:24) correct 62% (03:04) wrong based on 13

HideShow timer Statistics

Question 2
00:00
A
B
C
D
E

Question Stats:

67% (00:07) correct 33% (00:36) wrong based on 12

HideShow timer Statistics

Question 3
00:00
A
B
C
D
E

Question Stats:

45% (00:14) correct 55% (00:48) wrong based on 11

HideShow timer Statistics

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.

Which of the following can be inferred about uncoiled liquid crystals in an LCD pixel?

A They are opaque to ambient light.

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.
[Reveal] Spoiler: Question #1 OA
[Reveal] Spoiler: Question #2 OA
[Reveal] Spoiler: Question #3 OA

Kudos [?]: 2 [0], given: 3

Senior Manager
Senior Manager
User avatar
Joined: 07 Nov 2012
Posts: 333

Kudos [?]: 436 [0], given: 4

Schools: LBS '14 (A)
GMAT 1: 770 Q48 V48
Re: LEDs and LCDs [#permalink]

Show Tags

New post 08 Dec 2012, 12:30
Hi,

Let me see if I can help, here's my thought process...

Which of the following can be inferred about uncoiled liquid crystals in an LCD pixel?
OK. So need to scan through passage to find section talking about uncoiled liquid crystals and read that bit thoroughly...


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.


Found it. Now for the answer choices...

A They are opaque to ambient light. No, this doesn't work.. We're told as a FACT that it blocks light, we have no reason to assume ambient light is affected any differently to other light, so nothing inferred here.

B They are in a relaxed state, in comparison to their high-energy coiled state. No this is actually incorrect. We're told that crystals are relaxed in their coiled state

C They are found in one of two wave orientations, horizontal or vertical.No, these 2 orientations are mentioned, but not in relation to the liquid crystals

D They fail to rotate the polarization of surrounding photons enough to allow them to pass through nearby filters. Looks good. Correct. We are told that coiled crystals rotate to allow light photons through. We know uncoilded crystals do not allow light photons through, it is inferred that this is the reason why

E They cause the pixel to become transparent. No this doesn't work. We see something about opaque, nothing about any transparency

Hope it helps. James
_________________

Former GMAT Pill student, now on staff. Used GMATPILL OG 12 and nothing else: 770 (48,48) & 6.0



... and more

Kudos [?]: 436 [0], given: 4

Manager
Manager
User avatar
Joined: 31 Aug 2011
Posts: 224

Kudos [?]: 265 [0], given: 56

Re: LEDs and LCDs [#permalink]

Show Tags

New post 09 Dec 2012, 07:31
Which of the following can be inferred about uncoiled liquid crystals in an LCD pixel?

A They are opaque to ambient light.

a very nice distractor, It is surrounding filter which becomes opaque or transparent by the action of crystal not crystal itself

B They are in a relaxed state, in comparison to their high-energy coiled state.


This is opposite answer.

C They are found in one of two wave orientations, horizontal or vertical.
They make light photons polarized not get polarized themselves

D They fail to rotate the polarization of surrounding photons enough to allow them to pass through nearby filters.
A difficult but correct inference. Passage says the coiled ones in relaxed state allow light to pass through filters amd they act as transparent. And the uncoiled ones make filters opaque by doing something to polarization of light. what they do is mentioned in D .

E They cause the pixel to become transparent.

not transparent but opaque
_________________

If you found my contribution helpful, please click the +1 Kudos button on the left, I kinda need some =)

Kudos [?]: 265 [0], given: 56

Senior RC Moderator
User avatar
P
Status: It always seems impossible until it's done!!
Joined: 29 Aug 2012
Posts: 1063

Kudos [?]: 1597 [0], given: 281

Location: India
GMAT 1: 680 Q47 V34
WE: General Management (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Despite their acronymic similarity, LEDs and LCDs represent distinct [#permalink]

Show Tags

New post 03 Apr 2015, 02:05
1
This post was
BOOKMARKED
Part of New Project-->[url=http://gmatclub.com/forum/new-project-reading-comprehension-review-practice-195318.html]Reading Comprehension!!- Review/ Practice[/url]


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. 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.

[Reveal] Spoiler:
D


2. 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

[Reveal] Spoiler:
B


3. 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.

[Reveal] Spoiler:
C


_________________

Become a GMAT Club Premium member to avail lot of discounts

Kudos [?]: 1597 [0], given: 281

Non-Human User
User avatar
Joined: 01 Oct 2013
Posts: 10155

Kudos [?]: 275 [0], given: 0

Premium Member
Re: Despite their acronymic similarity, LEDs and LCDs represent [#permalink]

Show Tags

New post 13 Jun 2015, 20:29
Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

Kudos [?]: 275 [0], given: 0

Manager
Manager
avatar
B
Joined: 27 Dec 2014
Posts: 85

Kudos [?]: 60 [0], given: 98

Concentration: Leadership, Technology
Reviews Badge
Re: Despite their acronymic similarity, LEDs and LCDs represent distinct [#permalink]

Show Tags

New post 19 Jul 2015, 12:05
Hi - Can you please explain how the correct answer for Q3 is derived?
_________________

Cheers!
-----------------------------
Please give kudos if you think it is worth it !

Kudos [?]: 60 [0], given: 98

Re: Despite their acronymic similarity, LEDs and LCDs represent distinct   [#permalink] 19 Jul 2015, 12:05
Display posts from previous: Sort by

Despite their acronymic similarity, LEDs and LCDs represent distinct

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.