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Diameter of a telescope objective for a given angular resolution

This type of question, asked 2 times: 4 Apr 2026 S1, 8 Apr 2026 S2. All 2 questions below, oldest first.

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  1. Question 1

    4 Apr 2026 S1

    19
    A telescope with objective diameter R is used to observe a distant star emitting light of wavelength 500 nm , at a resolution of 5×10−75 \times10^{- 7} radian. The value of RR is ____\_\_\_\_ cm .

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  2. Question 2

    8 Apr 2026 S2

    22
    A distant star is to be observed by a telescope whose objective lens has diameter aa, at an angular resolution of 3.0×10−73.0 \times 10^{- 7} radian. If the wavelength of light from the star reaching the telescope is 500 nm , the minimum diameter of the objective lens of the telescope is ____\_\_\_\_ cm. (Nearest integer)