Light Emitting Diode Questions

Light Emitting Diodes (LEDs) are a type of semiconductor diode that emits light when an electric current is passed through it. This thin, flexible, and sometimes colourful strip is used as a light source in electronic devices and lighting fixtures. The light emitting diodes offer many benefits like low heat generation, energy efficiency, and long lifespan. These benefits make them perfect for use in homes that are looking to save money on their energy bills or businesses that want to cut down on their costs.

In the past, LEDs were primarily used as indicators in electronic devices. Nowadays, they are increasingly used as replacements for incandescent lamps and fluorescent lamps.

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Important Light Emitting Diode Questions with Answers

1. List five applications of LEDs.

The major five applications of LEDs:

LEDs are used in LED displays, TV Backlighting, Dimming of lights, Smartphone Backlighting, and Automotive Lighting.

2. In LEDs, light is emitted when ______.

1. Electrons recombine with electrons
2. Electrons recombine with holes
3. Electrons do not recombine
4. None of the above

Answer: b) Electrons recombine with holes

Explanation: When electrons recombine with holes, light is emitted from the LED.

3. Which of the following produce the current when it absorbs photons?

1. Transducer
2. LED
3. Photodiode
4. LCD

Answer: c) Photodiode

Explanation: Photodiode is a device that produces electricity when it absorbs photons.

4. Which of the following consume less power?

1. Light emitting diode
2. Incandescent light source

Answer: a) Light emitting diode

Explanation: Light emitting diode consumes less power, is smaller in size, and offers improved physical robustness.

5. List various types of LEDs.

Various types of LEDs are:

• Miniature LEDs
• High-Power LEDs
• Flash LED
• Bi and Tri-Colour
• Alphanumeric LED
• Lighting LED

6. Why is laser light said to be coherent?

Laser light is coherent since the wavelengths of the laser light are in phase in space and time.

7. LEDs work on the principle of ______.

1. Electromagnetic induction
2. Conduction
3. Electroluminescence
4. Induction

Answer: c) Electroluminescence

Explanation: Electroluminescence is an electrical and optical phenomenon where material emits light when electricity flows through it.

8. State true or false: High warm-up time is needed for LEDs.

1. TRUE
2. FALSE

Answer: b) FALSE

Explanation: little or no warm-up time is needed for light emitting diodes.

9. In local dimming, LEDs are dimmed _______.

1. Together
2. Independently

Answer: b) Independently

Explanation: In local dimming, LEDs are dimmed independently.

10. Aluminium alloys are used to obtain _______ light.

1. Red
2. Orange
3. Yellow
4. All of the above

Answer: d) All of the above

Explanation: Aluminium alloys are used to obtain yellow, orange, and red colour lights.

Practice Questions

1. What is a pin diode?
2. Explain how a diode works.
3. What determines the colour of a LED?
4. Is a laser a monochromatic light?
5. List the uses of LEDs.