a cross section of a parabolic reflector as shown below. a bulb is located at the focus the opening at the focus AB is 12cm what is the diameter of the opening CD 8cm from the vertex?

A10nc charge sits at a point in space where the magnitude of the electric field is 1500 n/c. what will the magnitude of the field be if the 10 nc charge is replaced by a 20 nc charge? assume the system is big enough to consider the charges as small test charges.