$A$ light beam is being reflected by using two mirrors,as in a periscope used in submarines. If one of the mirrors rotates by an angle $\theta$,the reflected light will deviate from its original path by the angle

An object is placed at a distance of $12\,cm$ in front of a plane mirror. $A$ virtual and erect image is formed by the mirror. Now,the mirror is moved by $4\,cm$ towards the stationary object. The distance by which the position of the image would be shifted is:

As shown in the figure,a particle is placed at $O$ in front of a plane mirror $M$. $A$ man at $P$ can move along the path $PY$ and $PY'$. Which of the following is true?

$A$ boy of height $1.5\, m$ with his eye level at $1.4\, m$ stands before a plane mirror of length $0.75\, m$ fixed on the wall. The height of the lower edge of the mirror above the floor is $0.8\, m$. Then:

Assertion : If the angle between the two plane mirrors is $72^o$ and the object is asymmetrically placed between the two mirrors,then $5$ images of the object will be formed.
Reason : For a given system of mirrors,the total number of images formed due to successive reflection is equal to either $\frac{360^o}{\theta}$ or $\frac{360^o}{\theta} - 1$ accordingly as $\frac{360^o}{\theta}$ is odd or even respectively.

Two plane mirrors $AB$ and $AC$ are inclined at an angle $\theta = 20^{\circ}$. $A$ ray of light starting from point $P$ is incident at point $Q$ on the mirror $AB$,then at $R$ on mirror $AC$,and again at $S$ on $AB$. Finally,the ray $ST$ goes parallel to mirror $AC$. The angle which the ray makes with the normal at point $Q$ on mirror $AB$ is: (in $^{\circ}$)