Previous Year 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?
Both Statement I and Statement II are correct and Statement II explains Statement I
Both Statement I and Statement II are correct, but Statement II does not explain Statement I
Statement I is correct, but Statement II is not correct
Statement I is not correct, but Statement II is correct
Correct Answer: A
Detailed Solution
Statement I is correct. Among the Rare Earth Elements, elements such as Yttrium, Europium and Terbium are used as phosphors in display technologies. According to the Indian Bureau of Mines, Yttrium, Europium and Terbium are used as phosphors in computer and television displays.
IREL also identifies uses of Rare Earth Elements in television screens, computers and monitor displays. In particular, oxides of Europium and Yttrium are useful in producing colours in television and electronic screens.
Statement II is also correct. Compounds/phosphor systems involving Europium, Terbium and Yttrium possess important luminescent/phosphor properties. For example, Europium can provide red and blue emission, while Terbium is associated with green/yellow-green emitting phosphors.
This optical property explains Statement I. To produce different colours on a screen, such phosphors absorb energy and emit light at characteristic wavelengths. This is precisely why certain Rare Earth Elements are particularly useful in display technology.