JEE Main 2016 · 10 Apr · Shift 1 · Physics Q20

← JEE Main 2016 · 10 Apr · Shift 1

PhysicsSingle correct+4 / -1Question 20 of 90

Two stars are 10 light years away from the earth. They are seen through a telescope of objective diameter 30 cm. The wavelength of light is 600 nm. To see the stars just resolved by the telescope, the minimum distance between them should be (1 light year = $9.46\times10^{15}$ m) of the order of :

10^6

10^8

10^{11}

10^{10}

Answer and worked solution

Official answer: B

The limit of resolution is $\theta=\frac{1.22\lambda}D=\frac{1.22\times6\times10^{-7}}{0.3}=2.44\times10^{-6}$ rad. At 10 light years, $d=9.46\times10^{16}\times2.44\times10^{-6}\approx2.3\times10^{11}$ m, of the order of $10^8$ km.

Topics:Resolving power Optical instruments

← Previous question Next question →

JEE Main 2016 · 10 Apr · Shift 1, Physics question 20