Question

Two light bulbs are 2.0 m apart. From what distance can these light bulbs be marginally resolved by a small telescope with a 4.50 cm. Assume that the lens is limited only by diffraction and λ = 600 nm

Answer 1

Answer:

R = 1.2295 10⁵  m

Explanation:

After reading your problem they give us the diameter of the lens d = 4.50 cm = 0.0450 m, therefore if we use the Rayleigh criterion for the resolution in the diffraction phenomenon, we have that the minimum separation occurs in the first minimum of diffraction of one of the bodies m = 1 coincides with the central maximum of the other body

            θ = 1.22 λ / D

where the constant 1.22 leaves the resolution in polar coordinates and D is the lens aperture

             

how angles are measured in radians

          θ = y / R

where y is the separation of the two bodies (bulbs) y = 2 m and R the distance from the bulbs to the lens

            $\frac{y}{R} = 1.22 \frac{ \lambda}{D}$

            R = $\frac{ y \ D}{1.22 \lambda}$

let's calculate

            R = $\frac{ 2 \ 0.045}{ 1.22 \ 600 \ 10^{-9}}$

            R = 1.2295 10⁵  m