If we assume that the metallic plates are perfect conductors, the electric field in their interiors must vanish. given that the electric field e⃗ due to a charged sheet with surface charge +σ is given by e=σ2ϵ0, and that it points away from the plane of the sheet, how can the condition that the electric field in plate i vanishes be written?

here the charge density of metal plate is given as

now the electric field is given Gauss law

now here E = constant

so we will have

Since total area on both sides of plate will be double and becomes 2A

Now if we will find the electric field inside the metal plate

Then as we know that total charge inside the plate will always be zero

so we have

continuous conducting path for current, power supply

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.