Question

What is the main difference between LCD and LED displays?

• A. LCD displays require a backlight, while LED displays emit their own light.
• B. LCD displays offer better color accuracy, while LED displays are brighter and more energy-efficient.
• C. LCD displays are typically thinner and lighter, while LED displays offer faster refresh rates.
• D. LCD displays has environmental impact, while LED displays are portable.

Hint:

Remember: \textbf{LCD} = Liquid Crystal Display (the crystals control the light). \textbf{LED} = Light Emitting Diode (the diodes emit the light). This distinction is key, even though the term "LED TV" usually just means an LCD screen with an LED backlight.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The question asks for the fundamental principle that distinguishes LCD (Liquid Crystal Display) technology from LED (Light Emitting Diode) display technology.
Step 2: Detailed Explanation:
LCD (Liquid Crystal Display): An LCD panel is composed of a layer of liquid crystals sandwiched between two polarizers. The crystals themselves do not produce light. They act as tiny shutters that can either block light or allow it to pass through by changing their alignment when an electric voltage is applied. To be visible, an LCD screen must have a separate light source behind it, known as a backlight. In older monitors, this was a Cold Cathode Fluorescent Lamp (CCFL), and in modern "LED TVs," it's an array of LEDs used as a backlight.
True LED Displays (like OLED or MicroLED): In these displays, each individual pixel is a tiny light-emitting diode that produces its own light. There is no need for a separate backlight layer. When a pixel needs to be black, the LED is simply turned off, allowing for perfect blacks and very high contrast ratios.
Therefore, the core difference is that LCDs are a transmissive technology (controlling light from a backlight), while true LED displays are an emissive technology (creating their own light). Option 1 correctly captures this fundamental distinction. The other options describe performance characteristics (like brightness, efficiency, refresh rate) which can vary widely among different models of both technologies and are consequences of the main principle, not the principle itself.
Step 3: Final Answer:
The main operational difference is that LCDs modulate light from an external backlight, whereas the pixels in an LED display generate their own light.