2025Statement-I & Statement-II (Assertion-Reason Style)Clean Energy & Materials
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?
A.Both Statement I and Statement II are correct and Statement II explains Statement I
B.Both Statement I and Statement II are correct but Statement II does not explain Statement I
C.Statement I is correct but Statement II is not correct
D.Statement I is not correct but Statement II is correct
Explanation: * Statement I is correct: Rare earth elements like europium, terbium, and yttrium are standard components utilized in manufacturing flat-screen TVs and computer monitors. * Statement II is correct: These elements possess distinct phosphorescent (luminescent) properties, meaning they emit visible light when excited by energy. This property directly explains why they are used to generate vivid colors in display screens, making Statement II the correct explanation for Statement I.
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2024Statement-I & Statement-II (Assertion-Reason Style)Space Technology & Astronomy
Consider the following statements:
Statement-I: Giant stars live much longer than dwarf stars.
Statement-II: Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.
Which one of the following is correct in respect of the above statements?
A.Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
B.Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
C.Statement-I is correct, but Statement-II is incorrect
D.Statement-I is incorrect, but Statement-II is correct
Explanation: * Statement-I is incorrect: High-mass giant stars hold much hotter and denser internal cores than smaller dwarf stars. This intense internal pressure causes giant stars to burn through their foundational core hydrogen fuel supply at a drastically faster rate, causing them to have significantly shorter lifespans than dwarf stars. * Statement-II is correct: Because of their immense mass, density, and core temperature parameters, giant stars experience a much higher rate of fusion and nuclear reactions than dwarf stars. Thus, option (d) is correct.
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