An object is placed between two plane mirrors inclined at some angle to each other. If the number of images formed is $7$, then the angle of inclination is: (in $^{\circ}$)

The light rays from an object have been reflected towards an observer from a standard flat mirror. The image observed by the observer is:

$A$ beam of light from a source $L$ is incident normally on a plane mirror fixed at a certain distance $x$ from the source. The beam is reflected back as a spot on a scale placed just above the source $L$. When the mirror is rotated through a small angle $\theta$,the spot of the light is found to move through a distance $y$ on the scale. The angle $\theta$ is given by

$A$ thick plane mirror shows a number of images of the filament of an electric bulb. Of these,the brightest image is the

$A$ light ray is incident perpendicular to the plane of a mirror. The angle of reflection will be ......$^o$.

What should be the angle between two plane mirrors so that whatever be the angle of incidence,the incident ray and the reflected ray from the two mirrors are parallel to each other (in $^o$)?