phyiscs human eye

airkapp

A human eyeball is about 2 cm long and the pupil has a maximum diameter of about 5 mm. What is the speed of this lens?


f-stop = 2 cm / .5 cm

f-stop = 4

is this it?

I'm not sure if I found the right formula in my book

thanks

futb0l

what is f-stop..??
and dont you have to use SI units?