By increasing the aperture of the objective lens, wavelength of light, focal length of the objective lens and the resolving power of an astronomical telescope respectively (a) is not affected, increases, increases (b) decreases, increases, is not affected (c) increases, decreases, is not affected (d) is not affected, increases, decreases

Answer: (a). Resolving power of a telescope: RP = (D)/(1.22λ). Increasing aperture D: RP increases. Increasing wavelength λ: RP decreases. Focal length does not appear in the formula: RP is not affected. So the resolving power changes as: increases, decreases, is not affected, which is option (c).

By increasing the aperture of the objective lens, wavelength of… | MHT CET 2020 (19 Oct, Shift 2)

Q30MHT CET 2020 · 19 OCT · SHIFT 2Easy

Optical Instruments & the Eye

By increasing the aperture of the objective lens, wavelength of light, focal length of the objective lens and the resolving power of an astronomical telescope respectively

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Answer: (a)

Resolving power of a telescope: $RP = \dfrac{D}{1.22\lambda}$ .
Increasing aperture $D$ : $RP$ increases.
Increasing wavelength $\lambda$ : $RP$ decreases.
Focal length does not appear in the formula: $RP$ is not affected.
So the resolving power changes as: increases, decreases, is not affected, which is option (c).

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