With the help of a ray diagram,show the formation of an image by a convex lens when the object is placed between $F$ and $2F$. Write two characteristics of the image so formed.

If the magnification of a body of size $1\, m$ is $2$,what is the size of the image (in $m$)?

$(a)$ $A$ ray of light falls normally on a face of a glass slab. What are the values of angle of incidence and angle of refraction of this ray?
$(b)$ Light enters from air to a medium $X$. Its speed in medium $X$ becomes $1.5 \times 10^{8} \ m \ s^{-1}$. Speed of light in air is $3 \times 10^{8} \ m \ s^{-1}$. Find the refractive index of medium $X$.

If an object of $4 \, cm$ height is placed at a distance of $12 \, cm$ from a concave mirror,then its image is formed at a distance of $24 \, cm$ from the mirror and behind it. What will be the height of the image (in $, cm$)?

$A$ ray of light $XY$ is incident on a spherical mirror as shown in the diagram. Redraw the diagram and mark the normal,angle of incidence and angle of reflection.

Two plane mirrors are at right angles to each other. $A$ man stands between them and combs his hair with his right hand. In how many images will he be seen using his left hand?