Calculate maximal reflection (Lambertian)

Question

Given a surface point P at (1,0,0), a normal direction (1,1,0) as well as a point light source at (1,2,0). If we assume that the surface point P is perfectly diffuse, to what location would the light have to move to achieve a maximal reflection according to the formula for diffuse surfaces (Lambertian)?

I've tried by calculating the dot product between N and L2(a,b,c) and making it = 1 because of the max. reflection is achieved with cos(0) I think. But it didn't work because I couldn't find L2 please help.

Answer 1

To get maximal reflection from point P, we just need to put light source on normal from point P, so in parametric form (any t):

L = P + t * N(at P) = (1,0,0) + t * (1,1,0)