Q. The length of subnormal of parabola $y^{2} = 4ax$ at any point is equal to
A) $\sqrt{2}a$
B) $2\sqrt{2}a$
C) $\frac{a}{\sqrt{2}}$
D) $2a$
Explanation
(d)
$\because\ \ \ y^{2} = 4ax$
$\therefore\ \frac{dy}{dx} = \frac{2a}{y}$
Length of subnormal$= y\frac{dy}{dx} = y\frac{2a}{y} = 2a$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.