Question 88 from UPSC CSE 2025 - S&T

Question

Consider the following statements:
Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors.
Statement II: Some rare earth elements have phosphorescent properties.
Which one of the following is correct in respect of the above statements?

IASCODEX · Accepted Answer

Correct Option: A. Both Statement I and Statement II are correct and Statement II explains Statement I

Strategy: Recognizing that rare earth elements are prominent in modern electronics is key. Statement I matches textbook knowledge about their use in display screens. Statement II pinpoints the phosphorescent property, which underpins their use in such screens. The linkage is direct: their phosphorescence is the reason for their role in displays, so Statement II explains Statement I.

Key Info: Rare earth elements comprise 15 lanthanides plus scandium and yttrium. These elements are not particularly rare geologically but are seldom found in commercially viable concentrations. Their unique electronic configurations enable specialized properties:

* In display technologies (like flat TV and monitor screens), elements such as europium, terbium, and yttrium form phosphors—the materials that emit colored light in response to electrical stimulation. This process is phosphorescence, crucial for vibrant red, green, and blue colors in cathode ray tube (CRT) and modern LED/LCD screens.
* Europium compounds provide red phosphor; terbium, green; and yttrium is a host lattice. Gadolinium and cerium may also be used in certain phosphor materials.
* Phosphorescence refers specifically to a type of photoluminescence; after being energized, these compounds continue to emit visible light, enabling sustained brightness in screens.
* Beyond electronics, rare earth elements are essential in high-strength magnets (e.g., neodymium), catalytic converters, rechargeable batteries, lasers, defense systems, and hybrid vehicle components.
* Extraction and refining of rare earths present environmental and geopolitical challenges: China currently dominates global supply. International efforts focus on diversification and sustainable sourcing due to their technological and strategic importance.
* The phenomena of luminescence, including phosphorescence and fluorescence, is central to several REEs' utility in optics, medical imaging, and lighting devices.
* Rare earths have no widespread biological function, and their industrial usage is dictated chiefly by their unique chemical and optical properties.

IASCODEX · Answer

Option B: Both Statement I and Statement II are correct but Statement II does not explain Statement I

IASCODEX · Answer

Option C: Statement I is correct but Statement II is not correct

IASCODEX · Answer

Option D: Statement I is not correct but Statement II is correct

Consider the following statements: Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors. Statement II: Some rare earth elements have phosphorescent properties. Which one of the following is correct in respect of the above statements?

Consider the following statements:
Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors.
Statement II: Some rare earth elements have phosphorescent properties.
Which one of the following is correct in respect of the above statements?