The focus of a parabolic mirror is at a distance of 8cm from the center the mirror is 25cm deep find the diameter of the mirror.

Answer 1

x^2 = 4py, so
x^2 = 32y
at y=25, x^2 = 800, so x = 20√2 = 28.28

That's the radius, so the diameter is 56.56 cm