If the absolute refractive indices of water and glass are $\frac{4}{3}$ and $\frac{3}{2}$ respectively,then what will be the ratio of the velocity of light in water to that of glass?

$A$ thin lens has a focal length of $-12\, cm$. Is it a convex lens or a concave lens?

$(a)$ Write the relation between $u, v, f$ for lenses and for mirrors,where $u, v, f$ are object distance,image distance,and focal length respectively.
$(b)$ The magnification produced by a concave mirror is $m = +4$. Write the information about the image given by this statement.
$(c)$ Draw a ray diagram for the following and show the formation of the images in the case of a concave mirror when the object is placed:
$(i)$ Between the pole and the focus point.
$(ii)$ At the centre of curvature.

$A$ ray of light is incident on a plane mirror normally. What are the angle of incidence and the angle of reflection?

Draw a ray diagram showing the path of rays of light when it enters with oblique incidence: $(i)$ from air into water; $(ii)$ from water into air.

The mirror outside the driver's side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning "Vehicles in this mirror are closer than they appear". What is the reason for this warning?