Question

A plane mirror is placed along positive $x-$ axis facing along the positive $y-$ axis. The equation of a linear object is $x=y$. The equation of its image is

• A. $x=y$
• B. $x+y=0$
• C. $2x+y=0$
• D. None of these

Answer 1

The correct option is B $x+y=0$

The slope of image is
$m=\tan (-{45}^{\circ })=-1$
$\therefore y=mx$
(As crossing from origin)
$\therefore y=-x$ or $x+y=0$
Hence, the correct answer is option $\left(b\right)$.