Light-Emitting Diodes (LEDs)

Choose the Correct Answer

Correct Answer : Option c

Explanation
Statement 1 is correct: An LED is a diode that emits light. Blue light is preferentially scattered by the atmosphere, resulting in potentially unacceptable levels of light pollution for astronomical observations. Unfortunately, LED streetlights emit more blue light on a per-lumen basis than the high-pressure sodium street lights they are rapidly replacing. Botanists and horticulturalists, however, may choose to differ. For them, it is the red light from streetlights that is the problem. Depending on the species and various environmental factors, even low levels of light trespass from roadway and outdoor area luminaires can have harmful effects on both wild and domesticated plants. LED streetlights likewise emit more red light on a per-lumen basis than high-pressure sodium streetlights.

Statement 2 is correct: Per watt of power consumed, LEDs can produce up to 300 lumen (amount of visible light emitted per second) versus incandescent bulbs’ 16 lumen and fluorescent lamps’ 70 lumen. Together with their greater durability and light contrast, LEDs’ advantages translated to higher cost savings and less material waste. LEDs have several applications in industry, consumer electronics, and household appliances: from smartphones to TV screens, from signboards to ‘feeding’ plants light in greenhouses, from barcode scanners to monitoring air quality. LEDs can also produce a variety of colours or emit energy at higher and lower frequencies; LEDs can be ‘embedded’ in skin; and organic LEDs emit more light (albeit by a different mechanism). Researchers are also exploring more efficient LEDs made of materials called perovskites.