Question

A ray of light moving parallel to the X - axis gets reflected from a concave parabolic mirror whose equation is $y^2+4x=4$ The reflected ray must pass through the point

• A. $(1,0)$
• B. $(-1,0)$
• C. $(0,0)$
• D. $(-2,0)$

Answer 1

The correct option is C $(0,0)$

Here, if a ray of light moving parallel to $x$ -axis gets reflected from a concave parabolic mirror then, after reflection, it must passes through focus.

$c:y^2+4x=4$

$\Rightarrow y^2=-4x+4$

$\Rightarrow y^2=-4(x-1)$

Focus: $(-a+1,0)\equiv (0,0)$