JEE Main 2026 Apr 8 Shift 2, Physics Q22: Magnification

JEE Main2026Apr 8, Shift 2Physics

Some distance star is to be observed by some telescope of diameter of objective lens $a$ , at an angular resolution of $3.0 \times 1 0^{- 7}$ 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)

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Solution

Rayleigh criterion for a circular aperture: $θ_{m i n} = \frac{1.22 λ}{D}$ .

Solving for the aperture diameter:

$D = \frac{1.22 λ}{θ} = \frac{1.22 \times 500 \times 1 0 ^{- 9}}{3.0 \times 1 0 ^{- 7}}$

$= \frac{1.22 \times 500}{3.0} \times 1 0^{- 2} m = 203.33 \times 1 0^{- 2} m = 2.0333$ m $\approx 203$ cm.

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JEE Main 2026 Apr 8 Shift 2, Physics Q22: Magnification

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