The principal focus is represented by the letter F. The distance between the pole and the principle focus of a spherical mirror is called the  _____.

A long horizontal mirror is next to a vertical screen (see figure). Parallel light rays are falling on the mirror at an angle $\alpha$ from the vertical. If a vertical object of height $h$ is kept on the mirror at a distance $d>h$ $\tan \left(\alpha \right).$ The length of the shadow of the object on the screen would be.

A mirror is placed at an angled of $30°$ with respect to $y-$axis (see figure). A light ray travelling in the negative $y-$direction strikes the mirror. The direction of the reflected ray is given by the vector