A metal cube 1.0 cm on each side is sandwiched between two electrodes. The electrodes create a 0.0050N/C electric field in the metal. A current of 9.0 A passes through the cube, from the positive electrode to the negative electrode. Identify the metal. a-Tungsten
b-gold
c-silver
d-copper

This is Tungsten .

Explanation:

Electrical field E = V / l , V is potential diff and l is length

.005 = V / .01

V = .005 X .01 = 5 X 10⁻³ volts

I current = 9A

Resistance R = V / I

= 5 x 10⁻³ / 9

= 5.55 x 10⁻⁶ ohm .

To calculate resistivity :

R = ρ l / S , l is length , S is cross sectional area

5.55 x 10⁻⁶ = ρ x .01  / .01 x .01

ρ = 5.5 x 10⁻⁸

This is Tungsten .

neither accurate nor precise.

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.