What is the total change in angle of reflection when mirror is tilted by 80?

[leehom]

Light is shining on to a plane mirror at an angle of incidence of 270. If the plain mirror is tilted such that the angle of incidence is reduce by 80, what will be the total change in the angel of reflection from the original reflected light?

 

[mgb_phys]

The angle of incidence is normally defined from the normal ( that is a line coming out of the surface at right angles to it) an AoI of 270deg doesn't make sense.
With the above definition the light just reflects from the surface at the same angle of incidence that it hit it.