Max distance of resolution from 2 point sources of light

Cheezay

1. The problem statement, all variables and given/known data
Two point sources of light are separated by 4.91 cm. As viewed through a 12.1 μm diameter pinhole, what is the maximum distance from which they can be resolved if red light (λ = 690 nm) is used?


2. Relevant equations
sinθ = 1.22*(λ/D)

y= L*tan θ



3. The attempt at a solution
Using sinθ = 1.22*(λ/D) , I solve for θ. Then using θ I put it into the second equation,
y= L*tan θ.

I should then be able to solve for L, but the problem is i don't know what y is, or what value i can use for y. Any suggestions? Thanks in advance

Redbelly98

Have you drawn a diagram? Looks like L is the distance between the pinhole and the two sources, and θ is the angle between the two sources as viewed from the pinhole. What would that make y?

p.s., the small angle approximations θ ≈ sinθ ≈ tanθ may be used here.