Question

A ray of light passing through the point A(1,2,3), strikes the plane x + y + z = 12 at B and on reflection passes through point C(3, 5, 9). Coordinates of point B is-

• A. (7, 0, 9)
• B. (–7, 0, 19)
• C. (7, 1, 19)
• D. None

Answer 1

Answer: (B)

(–7, 0, 19)

Answer 2

Image of point (1, 2, 3) about x + y + z = 12 is (5, 6, 7)

B is point of intersection of line BC with the plane

x + y + z = 12

Equation of BC is $\frac { x - 5 } { 2 }$ = =

\ coordinats of B is (–7, 0, 19)