The focal length of a plane mirror is .......

$A$ mirror is inclined at an angle of $\theta$ with the horizontal. If a ray of light is incident at an angle $\theta$ with the mirror,then the reflected ray makes the following angle with the horizontal:

To obtain $3$ images using two plane mirrors, they should be placed at an angle of ....... $^o$.

Which of the following sets of letters does not show lateral inversion?

Two plane mirrors $A$ and $B$ are placed parallel to each other as shown in the figure. $A$ light ray is incident on mirror $A$ at an angle of $30^o$. The plane of incidence coincides with the plane of the figure. What is the maximum number of reflections (including the first one) the ray will undergo before emerging?

$A$ plane mirror makes an angle of $30^\circ$ with the horizontal. $A$ vertical ray is incident on the mirror. What is the angle between the mirror and the reflected ray in degrees?