The velocity of light in air is $3 \times 10^{8} \, m \, s^{-1}$. What is the velocity of light in water? (The absolute refractive index of water is $\frac{4}{3}$.)

$A$ dice is placed with one of its edges parallel to the principal axis between the principal focus $(F)$ and the centre of curvature $(C)$ of a concave mirror. Then the final image has the shape of

State the laws of reflection.

The ray diagram given below illustrates the experimental setup for the determination of the focal length of a converging lens using a plane mirror.
$(i)$ State the magnification of the image formed.
$(ii)$ Write two characteristics of the image formed.
$(iii)$ What is the name given to the distance between the object and the optical centre of the lens in the given diagram?

Where is the image formed when an object is placed at the principal focus $(F)$ in front of a convex lens?

An object is placed at the following distances from a concave mirror of focal length $15 \, cm$.
$(a)$ $10 \, cm$ $(b)$ $20 \, cm$ $(c)$ $30 \, cm$ $(d)$ $40 \, cm$
Which position of the object will produce:
$(1)$ Virtual image
$(2)$ $A$ diminished real image
$(3)$ An enlarged real image
$(4)$ An image of same size