Lennart's ray runs from the object's tip straight to the middle of the mirror. It did not arrive parallel, and it misses the focal point. Rules 1 and 2 say nothing about it.
One more special beam completes the toolkit: the beam aimed at the mirror's center point. Its reflection follows a law you have used since the plane mirror.
Aim a beam at the one point where the reference line of the diagram meets the mirror's surface.
At that point the mirror behaves like a tiny flat mirror, and the law of reflection does the work.
At the center point, the mirror's normal lies along the principal axis.
The law of reflection gives equal angles each side of the normal. So here it gives equal angles each side of the principal axis.
A ray arriving 20° above the axis reflects 20° below it.
The rule is the same for concave and convex mirrors: at the center point, equal angles each side of the axis.
A ray strikes a concave mirror at the point where the principal axis meets the surface, arriving 45° above the axis. Where does the reflected ray go?
The center ray reflects at an equal angle on the other side of the axis.
The arriving angle is 45° above the axis.
So the reflected ray leaves at 45° below the axis.
The reflected ray leaves at 45° below the principal axis.
A ray strikes a convex mirror at the point where the principal axis meets the surface, arriving 25° below the axis. Where does the reflected ray go?
The center ray rule is the same on a convex mirror: equal angles each side of the axis.
The arriving angle is 25° below the axis.
So the reflected ray leaves at 25° above the axis.
The reflected ray leaves at 25° above the principal axis.
A ray strikes a concave mirror at the point where the principal axis meets the surface, arriving 30° above the axis. Which describes the reflected ray?
A ray strikes a convex mirror at the point where the principal axis meets the surface, arriving 35° above the axis. Enter the angle of the reflected ray below the axis, in degrees.
Katla says: 'A ray that strikes a curved mirror where the principal axis meets the surface reflects at an equal angle on the other side of the axis.' Is Katla correct?
At the point where the principal axis meets the mirror's surface, the center ray obeys the equal angle rule. Why?
A ray strikes a concave mirror at the point where the principal axis meets the surface, arriving 28° above the axis. Enter the angle of the reflected ray below the axis, in degrees.
Which arriving ray reflects at an equal angle on the other side of the principal axis?