Question

A spy satellite uses a camera attached to telescope. The resolution of objects which are imaged on

the earth is 40 cm when using a 1m mirror. Assuming that the resolution is not limited by factors

other than the size of the telescope, if the size of the mirror were doubled to 2 m what would the

resolution of objects on earth be?

(a) 10 cm (b) 20 cm (c) 30 cm (d) 40 cm (e) Can’t tell from the information given

Answer 1

Given, Initial Resolution of objects on the earth ( R₁ ) = 40 cm

Initial size of the mirror ( D₁ ) = 1 m

Now the size of the mirror is doubled i.e., D₂ =  2 cm

Required resolution of objects on the earth = R₂ (let)

According Rayleigh criteria,

limit of Resolution (  ) =

and as there is an inverse relation between and D.

when the the size of mirror is doubled. So, limit of resolution also gets halved.

Therefore, Resolution of telescope will also gets half i.e., R2 = 20 cm