question_answer

A circle is drawn to pass through the extremeties of the latus ractum of the parabola \[{{y}^{2}}=8x\] and touching the directrix, then radius of this circle is-

A) \[2\sqrt{2}\]      

B)        4     

C) 2                     

D)        3

Correct Answer: B

Solution :

[b] Latus rectum is focal chord and every circle on a focal chord as its diameter touches the directrix. Therefore radius \[=\frac{8}{2}=4\]