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

What is the nature of the image formed by an object placed at a distance of $10 \text{ cm}$ in front of a concave mirror with a focal length of $20 \text{ cm}$?

$A$ ray of light $XY$ is incident on a mirror as shown in the figure. The angle of incidence for this ray is the angle between it and the line joining two other points in the figure. Name these two points and show the course of rays after reflection.

What is the focal length of a convex lens having power $+5.0 \,D$?

If you want to see an enlarged image of your face, which type of mirror will you use? Where will you place your face?

$(a)$ For the same angle of incidence $45^{\circ}$,the angle of refraction in two transparent media $I$ and $II$ is $20^{\circ}$ and $30^{\circ}$ respectively. Out of $I$ and $II$,which medium is optically denser and why?
$(b)$ Light enters from air to diamond,which has a refractive index of $2.42$. Calculate the speed of light in diamond,if the speed of light in air is $3.00 \times 10^{8} \text{ m s}^{-1}$.