1. Which of the following statements concerning nuclear fission is correct? a. Neutrons are both reactants and products in the fission process
b. Uranium-238 is the most important fissionable radioisotope
C. A number of diagnostic procedures in nuclear medicine are now based on
nuclear fission
d. More than one correct response
e. No correct response

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.

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray