What is the definition of the half-life of a radioactive isotope? A. The time it takes for half the parent nuclei in a sample to become
daughter nuclei
B. The time it takes for all the parent nuclei in a sample to become
daughter nuclei
C. The time it takes for all the daughter nuclei in a sarnple to become
parent nuclei
D. The time it takes for half the daughter nuclei in a sample to
become parent nuclei

Half-life is the amount of time it takes for the initial mass of the isotope to decompose, by half, into other lighter atoms.

Explanation:Different radioactive isotopes have different half-lives. For example, the element technetium-99m has a half life of 6 hours. This means that is 100 kg of the element is left to decay, in 6 hours, 50kg of the mass will have changed into other elements/atoms. The half-life of uranium-238 is 4.5 billion years while that of polonium-216 is only 0.145 seconds.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.

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.