An object is initially at a distance of $100 \; cm$ from a plane mirror. If the mirror approaches the object at a speed of $10 \; cm/s$,then after $6 \; s$,the distance between the object and its image will be: (in $; cm$)

The incident ray,reflected ray,and the outward drawn normal are denoted by the unit vectors $\overrightarrow{ a }, \overrightarrow{ b }$ and $\overrightarrow{ c }$ respectively. Choose the correct relation for these vectors.

$A$ point source of light $S$,placed at a distance $60 \,cm$ in front of the centre of a plane mirror of width $50 \,cm$,hangs vertically on a wall. $A$ man walks in front of the mirror along a line parallel to the mirror at a distance $1.2 \,m$ from it (see in the figure). The distance between the extreme points where he can see the image of the light source in the mirror is $\ldots \ldots \ldots \,cm.$

Light of wavelength $5000 \,\mathring{A}$ falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light? For what angle of incidence is the reflected ray normal to the incident ray?

Two plane mirrors are kept on a horizontal table making an angle $\theta$ with each other as shown schematically in the figure. The angle $\theta$ is such that any ray of light reflected after striking both the mirrors returns parallel to its incident path. For this to happen,the value of $\theta$ should be (in $^{\circ}$)

When a plane mirror is placed horizontally on a level ground at a distance of $60 \ m$ from the foot of a tower,the top of the tower and its image in the mirror subtend an angle of $90^\circ$ at the eye. The height of the tower will be.....$m$.