An object is placed at a distance of $50 \mathrm{cm}$ in front of a convex mirror of focal length $25 \mathrm{cm}$. Find the image distance. What will be its nature?

An object is placed at a distance of $15 \mathrm{cm}$ in front of a concave mirror of focal length $30 \mathrm{cm}$. Find the nature and position of the image?

An object is placed at a distance of $15 \mathrm{cm}$ in front of a convex mirror of focal length $30 \mathrm{cm}$. Find the nature and position of the image.

In which medium will light travel faster, water or kerosene?

If the refractive index of glass is $1.5$, what will be the apparent thickness (in centimetres) of a glass plate of $1.5 \mathrm{cm}$ thick?

A lens can focus a real image having the same size as the object on a screen $1 \mathrm{m}$ away from the lens. What is the focal length (in metres) of the lens?

An object is seen magnified through a lens. What is the type of the lens- convex or concave?

An object is seen always diminished through a lens. What is the type of lens- convex or concave?