A. Because the line of the angle of incidence is always equal to the line and angle of reflection.
Take the last figure—CD is much larger than the mirror AB; but the head of the arrow C is reflected obliquely behind the mirror to G; and the barb D appears at H.—Why? Because the line CA=AG and the angle CAB=angle GAB, &c. The same may be said of the point D.
Q. Why does a shadow in water always appear topsy-turvy?
A. Because the line of the angle of incidence is always equal to the line and angle of reflection.
Here the arrow-head A strikes the water at F, and is reflected to D; and the barb B strikes the water at E, and is reflected to C.
If a spectator stands at G, he will see the reflected lines CE and DF, produced as far as G.
It is very plain that the more elevated object A will strike the water, and be projected from it more perpendicularly than the point B, and therefore the shadow will seem inverted.
Q. When we see our shadow in water, why do we seem to stand on our head?
A. Because the line of the angle of incidence is always equal to the line and angle of reflection.
Suppose our head to be at A, and our feet at B; then the shadow of our head will be seen at D, and the shadow of our feet at C. (See last figure.)