Question

Two light bulbs are 0. 900 mm apart. from what distance can these light bulbs be marginally resolved by a small telescope with a 4. 30 cmcm -diameter objective lens?

Answer 1

Rayleigh's criterion for resolution is

θ = 1.22 * λ / D

If we choose green light (near the middle of the spectrum)

λ = 5000 * 1.0E-10 = 5.0E-7 m

Since D = .043 m aperature available for resolution

θ = 1.22 * λ / D = 1.22 * 5.0E-7 / .043 = 1.4E-5

D = S * θ where θ is angle subtended by D

S = D / θ = .0009 m / 1.4E-5 = 64 m

S = 64 m