# Thread: Planes and Lines II

1. ## Planes and Lines II

Question 2: A lightbeam that originates from the point (3, -2, -1) is mirrored on the plane x - 2y -2z = 0. The mirrored lightbeam goes through the point (4, -1, -6). In what point did the lightbeam hit the plane?

2. ## Re: Planes and Lines II

Originally Posted by accordingplum
Question 2: A lightbeam that originates from the point (3, -2, -1) is mirrored on the plane x - 2y -2z = 0. The mirrored lightbeam goes through the point (4, -1, -6). In what point did the lightbeam hit the plane?
This appears to be exactly like problem #1. One more dimension, sure, but otherwise identical. Can you find a Normal Vector to the Plane?

3. ## Re: Planes and Lines II

$M$ is the projection of $\displaystyle L(3,-2,-1)$ onto the plane $\displaystyle x-2y-2z=0$

$N$ is the projection of $\displaystyle Q(4,-1,-6)$ onto the same plane

Hit the plane at $P$