1. If a parabolic reflector is 20 cm in diameter and 5 cm deep, find the focus.
Le the parabolic reflector opens towards the right.
So the equation of parabolic reflector will be,
Now, Since this curve will pass through the point (5,10) if we assume origin at the optical centre,
Hence, The focus of the parabola is,
As we know on any concave curve
Hence the focus is 5 cm right to the optical centre.