When sun directly shines thru the window - I can see small specs of dusts in the air. All specs have different sizes.
Assuming direct sun luminosity is 100kLux, spec is a perfect sphere, reflection is isotropic, what is the smallest spec of dust I can see from 20cm?
Could I see smaller particles if I increase light intensity?
What is the absolute minimum of the object size given infinitely powerful light source? Will it be the quantum physics that places limits?