Question
A ray of light moving parallel to the $$x$$-axis gets reflected from a parabolic
mirror whose equation is $${\left( {y - 2} \right)^2} = 4\left( {x + 1} \right).$$ After reflection, the ray must pass through the point :
A.
$$\left( {0,\,2} \right)$$
B.
$$\left( {2,\,0} \right)$$
C.
$$\left( {0,\, - 2} \right)$$
D.
$$\left( {-1,\,2} \right)$$
Answer :
$$\left( {0,\,2} \right)$$
Solution :
The equation of the axis of the parabola is $$y - 2 = 0,$$ which is parallel to the $$x$$-axis. So, a ray parallel to the $$x$$-axis is parallel to the axis of the
parabola. We know that any ray parallel to the axis of a parabola passes through the focus after reflection. Here $$\left( {0,\,2} \right)$$ is the focus.