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?
ABoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
BBoth Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
CStatement-I is correct, but Statement-II is incorrect
DStatement-I is incorrect, but Statement-II is correct
Answer & Solution
Correct answer: D. Statement-I is incorrect, but Statement-II is correct
Answer: D. Statement-I is INCORRECT; Statement-II is CORRECT.
Statement-I: 'Giant stars live longer than dwarf stars' is FALSE. The relationship is opposite. Stellar lifetime depends on fuel mass divided by fuel consumption rate. Although giant stars (high mass) have MORE fuel, they burn it at a vastly HIGHER RATE due to higher core temperatures and pressures. Net effect: GIANT stars live for MILLIONS of years; DWARF stars (like red dwarfs) live for BILLIONS of years.
Statement-II: 'Giant stars have a greater rate of nuclear reactions' is CORRECT. The hotter, denser cores of massive giant stars drive much faster nuclear fusion. This is precisely why they exhaust their fuel quickly despite having more of it.
Statement II is correct and is actually the REASON why Statement I is wrong.
Source: NCERT Class 11 Geography Ch 1 (Universe and Solar System) / NASA stellar evolution references.
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