The absolute refractive indices of water,glass,and diamond are $1.33$,$1.50$,and $2.42$ respectively. Which medium is the most optically dense?

Which of the following statements is true?

$A$ $2.0 \text{ cm}$ 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.

Where should an object be placed in front of a concave mirror to obtain a real and diminished image?

With respect to air,the refractive indices of ice and rock salt are $1.31$ and $1.54$ respectively. Calculate the refractive index of rock salt with respect to ice.

At what position should an object be placed in front of a concave mirror to obtain a magnification of $(- 2)$?