LCD screen

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Quick Questions

Shade in the A or B circle for each question.

1. What lights up an LCD screen so you can see the picture?

A A backlight shining through the panel

B Each pixel makes its own light

2. What do the liquid crystals in an LCD do?

A Glow to give off their own light

B Twist to block or let through light

3. Which colour filters does each LCD pixel use?

A Red, green and blue

B Cyan, magenta and yellow

4. Which statement about an LCD screen is correct?

A The backlight is always behind the liquid crystal layer

B The backlight is in front of the liquid crystal layer

5. How does an LCD pixel show a darker colour?

A The backlight is removed from that one pixel

B Crystals twist to let less light pass through the filter

Match the Pairs

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

Left column		Right column
1LCD screen		ARed, green and blue filters on each pixel that colour the light passing through the liquid crystals
2RGB colour filters		BAn LCD pixel does not make light itself. A backlight shines through the liquid crystals and the colour filters.
3The backlight shines through the panel, and the liquid crystals twist to let through more or less of that light		CLiquid crystals are not the light source. They twist to control how much backlight passes through each pixel.
4LCD screens are used in monitors, TVs and laptops		DA screen where a backlight shines through liquid crystals that block or pass light to make each pixel's colour
5An LCD screen makes its own light from each pixel		Ebacklight -> liquid crystals -> colour filters
6Liquid crystals in an LCD are the backlight		FLCD = [monitor, TV, laptop]

Definitions

LCD screen

Fill in the Blanks

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

lightSource ← _________

IF voltage = ON THEN crystals._____() ENDIF

filtersPerPixel ← _

FOR pixel ← 1 TO totalPixels mix(red, green, ____) NEXT pixel

lcdUses ← ["monitor", "TV", "laptop"] OUTPUT ______(lcdUses)

Spot the Error

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

Question 1

A screen ← LCD

B backlight ← OFF

C light shines through crystals

Question 2

A FOR EACH pixel IN panel

B light ← room light

C NEXT pixel

Question 3

A uses ← monitors, TVs, speakers

B backlight ← ON

C crystals twist per pixel

Question 4

A FOR EACH pixel IN backlight

B set red/green/blue filters

C NEXT pixel

Question 5

A backlight ← ON

B light shines through crystals

C crystals twist: block or pass

D pixel colour ← white filter

Answer Key

LCD screen

Section A: Quick Questions

A — A backlight shining through the panel

B — Twist to block or let through light

A — Red, green and blue

A — The backlight is always behind the liquid crystal layer

B — Crystals twist to let less light pass through the filter

Section B: Match the Pairs

LCD screen → A screen where a backlight shines through liquid crystals that block or pass light to make each pixel's colour

RGB colour filters → Red, green and blue filters on each pixel that colour the light passing through the liquid crystals

The backlight shines through the panel, and the liquid crystals twist to let through more or less of that light → backlight -> liquid crystals -> colour filters

LCD screens are used in monitors, TVs and laptops → LCD = [monitor, TV, laptop]

An LCD screen makes its own light from each pixel → An LCD pixel does not make light itself. A backlight shines through the liquid crystals and the colour filters.

Liquid crystals in an LCD are the backlight → Liquid crystals are not the light source. They twist to control how much backlight passes through each pixel.

Section C: Definitions

LCD screen — Screen with a backlight shining through liquid crystals that twist to block or pass light. Red, green and blue filters on each pixel make its colour.

Section D: Fill in the Blanks

lightSource ← backlight

IF voltage = ON THEN
  crystals.twist()
ENDIF

filtersPerPixel ← 3

FOR pixel ← 1 TO totalPixels
  mix(red, green, blue)
NEXT pixel

lcdUses ← ["monitor", "TV", "laptop"]
OUTPUT LENGTH(lcdUses)

Section E: Spot the Error

B — An LCD makes no light of its own. The backlight must be ON so light can shine through the liquid crystals. It should be backlight ← ON.

B — The light that passes through each pixel comes from the screen's own backlight, not from room light. It should be light ← backlight.

A — LCD screens are used in monitors, TVs and laptops. A speaker is an output device that makes sound, so it has no LCD screen.

A — The pixels are part of the LCD panel (the screen), not the backlight. The loop should be FOR EACH pixel IN screen.

D — Each pixel gets its colour from red, green and blue filters, not a single white filter. It should be pixel colour ← RGB filters.