What do you understand by the terms
$(i)$ Real image?
$(ii)$ Virtual image?

What changes; frequency or wavelength, when light passes from a rarer to a denser medium?

What type of image is formed by a plane mirror?

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

$(a)$ Water has a refractive index of $1.33$ and alcohol has a refractive index of $1.36$. Which of the two media is optically denser? Give a reason for your answer. Draw a ray diagram to show the path of a ray of light passing obliquely from water to alcohol.
$(b)$ The absolute refractive index of diamond is $2.42$ and the absolute refractive index of glass is $1.50$. Find the refractive index of diamond with respect to glass.

Find the focal length of a convex lens,if its power is $+2.0 \ D$. (in $m$)