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UPSC Prelims 2025 GS Paper 1, question 81

Topic: Science and technology

Q81

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?

  1. (a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-ICorrect answer
  2. (b) Both Statement-I and Statement-II are correct but Statement-II does not explain Statement-I
  3. (c) Statement-I is correct but Statement-II is not correct
  4. (d) Statement-I is not correct but Statement-II is correct

Solution.

Answer: (a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

  1. Statement-I is correct: rare earth elements (such as Europium, Terbium, Yttrium, and Cerium) are essential components in the manufacture of flat-panel television screens, LED backlights, and computer monitors.
  2. Statement-II is correct and explains Statement-I: because trivalent rare earth ions exhibit sharp, intense phosphorescent/luminescent emissions across red (Europium), green (Terbium), and blue (Cerium/Europium) wavelengths, they are used as display phosphors.