Which of the following statements is true about the image formed by a plane mirror?

How many times is the velocity of light in a vacuum compared to the velocity of light in water?

$A$ $2.0 \text{ cm}$ tall object is placed perpendicular to the principal axis of a convex lens of focal length $10 \text{ cm}$. The distance of the object from the lens is $15 \text{ cm}$. Find the position,nature,and size of the image formed.

Refractive index of diamond with respect to glass is $1.6$ and absolute refractive index of glass is $1.5$. Find out the absolute refractive index of diamond.

Two lenses of power $+3.5 D$ and $-2.5 D$ are placed in contact. Find the power and focal length of the lens combination.

Write the relationship between object distance $(u)$,image distance $(v)$,and focal length $(f)$ for a spherical mirror.