LED screen

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Quick Questions

Shade in the A or B circle for each question.

1. What does an LED screen use as its light source?

A Cold cathode fluorescent lamps

B Light emitting diodes

2. Most LED TVs and phone screens are best described as:

A An LCD panel lit by LED backlights

B A screen with no LCD panel and no backlight at all

3. Which statement about LED screens is correct?

A They can be thinner than older backlit screens

B They must be thicker because LEDs are large

4. Compared with older backlights, LED backlights use:

A Less power

B More power

5. In some LED screens, what do the LEDs act as?

A Only the screen's speakers

B The pixels themselves

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1LED-backlit LCD		ALED stands for Light Emitting Diode, not Liquid Emitting Display. The diode is the light source.
2LED backlight		Bscreen.thickness = thin
3An LED screen is thinner than an older screen with a bulb backlight because LEDs are tiny		CLED screens use LOW power, not high power. This is one advantage over older backlights.
4Big outdoor billboards can use LEDs as the pixels themselves, so each pixel makes its own light		Dpixel = LED
5LED screen: power use = very high		EA bright, thin light source made of light emitting diodes that uses less power than older backlights
6LED = Liquid Emitting Display		FAn LCD panel that has a layer of light emitting diodes behind it to light up the picture

Definitions

LED screen

Fill in the Blanks

Complete each line of code by filling in the missing parts.

______ "LED screens are bright and thin"

__ backlight = "LED" THEN

IF powerUse = "low" ____ OUTPUT "LED backlight saves energy" ENDIF

IF type = "LED" ___ thin = TRUE THEN OUTPUT "Slim LED TV" ENDIF

IF pixels = "LED" THEN OUTPUT "Billboard screen" _____

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A screen = "LED"

B panel = "LCD"

C light_source = "fluorescent tube"

Question 2

A backlight == "LED"

B if backlight == "LED":

C power = "low"

D print(power)

Question 3

A thickness_mm = 8

B thin = thickness_mm > 10

C if thin:

D print("LED is thin")

Question 4

A uses = []

B uses.append("TV")

C uses.append("phone")

D uses.add("billboard")

Question 5

A led_watts = 40

B old_watts = 100

C saving = led_watts - old_watts

D print(saving)

Answer Key

LED screen

Section A: Quick Questions

B — Light emitting diodes

A — An LCD panel lit by LED backlights

A — They can be thinner than older backlit screens

A — Less power

B — The pixels themselves

Section B: Match the Pairs

LED-backlit LCD → An LCD panel that has a layer of light emitting diodes behind it to light up the picture

LED backlight → A bright, thin light source made of light emitting diodes that uses less power than older backlights

An LED screen is thinner than an older screen with a bulb backlight because LEDs are tiny → screen.thickness = thin

Big outdoor billboards can use LEDs as the pixels themselves, so each pixel makes its own light → pixel = LED

LED screen: power use = very high → LED screens use LOW power, not high power. This is one advantage over older backlights.

LED = Liquid Emitting Display → LED stands for Light Emitting Diode, not Liquid Emitting Display. The diode is the light source.

Section C: Definitions

LED screen — A screen that uses light emitting diodes as its light source, as a backlight for an LCD panel or as the pixels themselves. It is bright, thin and uses little power.

Section D: Fill in the Blanks

OUTPUT "LED screens are bright and thin"

IF backlight = "LED" THEN

IF powerUse = "low" THEN
  OUTPUT "LED backlight saves energy"
ENDIF

IF type = "LED" AND thin = TRUE THEN
  OUTPUT "Slim LED TV"
ENDIF

IF pixels = "LED" THEN
  OUTPUT "Billboard screen"
ENDIF

Section E: Spot the Error

C — An LED screen uses light emitting diodes as its light source. Fluorescent tubes were used in older LCD backlights. Line 3 should be light_source = "diodes".

A — Line 1 uses == (comparison) instead of = (assignment). backlight is never given a value, so the program crashes. It should be backlight = "LED".

B — LEDs give thinner screens, so a thin screen has a small thickness. Using > makes thin False for 8 mm. Line 2 should use < 10.

D — Python lists do not have an add method. Use append to add LED screen uses such as TVs, phones and billboards. Line 4 should be uses.append("billboard").

C — LED backlights use less power than older backlights. The saving is old power minus LED power. The broken line gives a negative saving. It should be old_watts - led_watts.