Question

LEDs used in electronic devices emit:

• A. X-rays
• B. Ultraviolet light
• C. Radio waves
• D. Visible light

Hint:

Think about the everyday coloured indicator lights you see glowing on chargers, remotes and displays.

Answer 1

The Correct Option is D

Step 1: An LED, short for light emitting diode, is a semiconductor device made from a p-n junction, usually built from compound semiconductors such as gallium arsenide or gallium phosphide combinations.

Step 2: When the LED is connected in forward bias, electrons from the n-region and holes from the p-region are pushed toward the junction, where they combine with each other.

Step 3: Each time an electron falls into a hole and recombines, it releases the extra energy it was carrying, and in an LED this energy is released as a photon of light rather than as heat, a process called electroluminescence.

Step 4: The exact colour of light emitted depends on the energy gap of the particular semiconductor material used, and LEDs are manufactured so that this energy gap corresponds to photons in the visible range, giving the familiar red, green, blue and other coloured LED lights used in indicator lamps, displays and torches.

Step 5: So the light commonly emitted by LEDs in everyday electronic devices is visible light, option D.