Questions

Hard disk is the secondary storage device, which holds the data in bulk, and it holds the data on the magnetic medium of the disk.Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files.

The resistivity of wire or the metal conductor is depend on the number density of free electrons in the conductor. so its mainly depends on nature of the material

Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.

Resistivity :

Resistivity is a measure of the resistance to the flow of electrons. 

Conductivity :

Conductivity is just the inverse of resistivity, σ = 1/ρ, where σ is conductivity and ρ is resistivity.

Example:

Think of a pipe and water, the bigger the pipe, the easier water can flow and thus the lower the resistance. 

Refractive Index of glass with respect to water can be calculated by 

(Refractive Index of glass with respect to air) × (1/Refractive Index of water with respect to air)

We know that,

Refractive Index of glass with respect to air = 4/3

Refractive index of water with respect to air = 3/2

Hence, Refractive Index of glass with respect to water = (4/3) x (2/3) = 8/9.