Which of the following processes will not strengthen a metal? group of answer choices
a. increasing the dislocation density
b. solid-solution alloying with an interstitial impurity
c. solid-solution alloying with a substitutional impurity
d. adding a second phase precipitate
e. increasing the grain size
f. all of the above will strengthen a metal
g. none of the above will strengthen

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.

the right answer is 0.3 meters per second