Question

When LED is manufactured by using aluminium gallium arsenide (AlGaAs), it emits

• A. ultra-violet light
• B. infra red radiation
• C. green light
• D. blue light

Hint:

AlGaAs is commonly used in remote controls and infrared sensors because of its specific emission wavelength.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The color or wavelength of light emitted by an LED depends on the bandgap energy of the semiconductor material used to make it.
Step 3: Detailed Explanation:
Aluminium Gallium Arsenide (\(Al_{x}Ga_{1-x}As\)) is a common semiconductor used in light emitting diodes.
Depending on the proportion of Aluminium (\(x\)), it can emit light ranging from visible red to infra-red.
Specifically, pure Gallium Arsenide (\(GaAs\)) has a bandgap that emits in the infra-red region. Adding Aluminium can shift this towards the visible red region.
In the context of standard options provided in textbooks and exams, \(AlGaAs\) is primarily associated with efficient infra-red and high-brightness red LEDs.
Given the choices, infra-red is the correct standard classification for this material group.
Step 4: Final Answer:
AlGaAs LEDs emit infra-red radiation.