 Hello and welcome to the session. Let us discuss the following question. It says if a parabolic reflector is 20 cm in diameter and 5 cm deep, find its focus. Let us first understand what is a parabola. A parabola is a set of all points in a plane that are equidistant from a fixed line and a fixed point in the plane and that fixed point is the focus. So let us now move on to the solution and the general equation of the parabola given by why its focus is the point A0. So to find the focus we need to find A. Now we are given that the diameter of reflector is 20 cm, is PQ 20 cm and it is equal to 2 y because this much distance is y therefore the total is 2 y. So the radius is half of it that is say this point as m is 10 cm it is equal to y and we are also given that the reflector is 5 cm deep that is this much distance is 5 cm. So here x is 5 cm that is the length of 8p dash. Now to find the value of A we substitute the value of x and y in the equation of parabola. So from 1 we have which is 5. So this implies A is equal to 100 upon 20 equal to 5 hence the focus is at the point 50. Now the distance of the focus 50 from vertex that is from 00 is 5 cm which is same as the length of the focus lies on the diameter. At the point diameter touches the x axis and this point is the midpoint of the given diameter hence focus at the midpoint of the given diameter. And this completes the question. Bye for now. Take care.