Does optically denser medium mean greater mass per unit volume?

If S is the stress and Y is young's modulus of the material of a wire , then the energy stored in the wire per unit volume is

The densities of two substance are 2:3 and their specific heats are 0.12 and 0.09 respectively.compare their capacities per unit volume.

Two wires of same radius and legth are subjected to the same load . One wire is of steel an the other is of copper . If the young modulus of steel is twice that of copper find the ratio of elastic energy stored per unit volume in steel to that of copper .

Relation between prepssure P and average kinetic energy E per unit volume of a gas is

An expression of physical quantity is written as X = sqrtfrac(T)(M) , where T is the applied force and m is the mass per unit length. Find the dimensional representation of X and identify. The physical quantity. ( X = sqrtfrac(T)(m) .